Modified cellulose from chemical kraft fiber and methods of making and using the same

ABSTRACT

A modified kraft pulp fiber with unique properties is provided. The modified fiber can be a modified bleached kraft fiber that is almost indistinguishable from its conventional counterpart, except that it has a low degree of polymerization (DP). Methods for making the modified fiber and products made from it are also provided. The method can be a one step acidic, iron catalyzed peroxide treatment process that can be incorporated into a single stage of a multi-stage bleaching process. The products can be chemical cellulose feedstocks, microcrystalline cellulose feedstocks, fluff pulps and products made from them.

This application is a U.S. national stage entry under 35 U.S.C. §371from PCT International Application No. PCT/US2010/036763, filed May 28,2010, and claims priority to and the benefit of the filing date of U.S.Provisional Application No. 61/182,000, filed May 28, 2009, the subjectmatter of all of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to the chemical modification of cellulose fiber.More particularly, this disclosure relates to chemically modifiedcellulose fiber derived from bleached kraft pulp that exhibits a uniqueset of characteristics, improving its performance over standardcellulose fiber derived from kraft pulp and making it useful inapplications that have heretofore been limited to expensive fibers(e.g., cotton or high alpha content sulfite pulp). Specifically, thechemically modified bleached kraft fiber may exhibit one or more of thefollowing beneficial characteristics, including but not limited to,improved odor control, improved compressibility, and/or improvedbrightness. The chemically modified bleached kraft fiber may exhibit oneor more of these beneficial characteristics while also maintaining oneor more other characteristics of the non-chemically modified bleachedkraft fiber, for example, maintaining fiber length and/or freeness.

This disclosure further relates to chemically modified cellulose fiberderived from bleached softwood and/or hardwood kraft pulp that exhibitsa low or ultra low degree of polymerization, making it suitable for useas fluff pulp in absorbent products, as a chemical cellulose feedstockin the production of cellulose derivatives including cellulose ethersand esters, and in consumer products. As used herein “degree ofpolymerization” may be abbreviated “DP.” This disclosure still furtherrelates to cellulose derived from a chemically modified kraft fiberhaving a level-off degree of polymerization of less than about 80. Morespecifically, the chemically modified kraft fiber described herein,exhibiting a low or ultra low degree of polymerization (herein referredto as “LDP” or “ULDP”), can be treated by acid or alkaline hydrolysis tofurther reduce the degree of polymerization to less than about 80, forinstance to less than about 50, to make it suitable for a variety ofdownstream applications.

This disclosure also relates to methods for producing the improved fiberdescribed. This disclosure provides, in part, a method forsimultaneously increasing the carboxylic and aldehydic functionality ofkraft fibers. The fiber, described, is subjected to a catalyticoxidation treatment. In some embodiments, the fiber is oxidized withiron or copper and then further bleached to provide a fiber withbeneficial brightness characteristics, for example brightness comparableto standard bleached fiber. Further, at least one process is disclosedthat can provide the improved beneficial characteristics mentionedabove, without the introduction of costly added steps for post-treatmentof the bleached fiber. In this less costly embodiment, the fiber can betreated in a single stage of a kraft process, such as a kraft bleachingprocess. Still a further embodiment relates to a five-stage bleachingprocess comprising a sequence of D₀E1D1E2D2, where stage four (E2)comprises the catalytic oxidation treatment.

Finally, this disclosure relates to consumer products, cellulosederivatives (including cellulose ethers and esters), andmicrocrystalline cellulose all produced using the chemically modifiedcellulose fiber as described.

BACKGROUND

Cellulose fiber and derivatives are widely used in paper, absorbentproducts, food or food-related applications, pharmaceuticals, and inindustrial applications. The main sources of cellulose fiber are woodpulp and cotton. The cellulose source and the cellulose processingconditions generally dictate the cellulose fiber characteristics, andtherefore, the fiber's applicability for certain end uses. A need existsfor cellulose fiber that is relatively inexpensive to process, yet ishighly versatile, enabling its use in a variety of applications.

Cellulose exists generally as a polymer chain comprising hundreds totens of thousands of glucose units. Various methods of oxidizingcellulose are known. In cellulose oxidation, hydroxyl groups of theglycosides of the cellulose chains can be converted, for example, tocarbonyl groups such as aldehyde groups or carboxylic acid groups.Depending on the oxidation method and conditions used, the type, degree,and location of the carbonyl modifications may vary. It is known that,certain oxidation conditions may degrade the cellulose chainsthemselves, for example by cleaving the glycosidic rings in thecellulose chain, resulting in depolymerization. In most instances,depolymerized cellulose not only has a reduced viscosity, but also has ashorter fiber length than the starting cellulosic material. Whencellulose is degraded, such as by depolymerizing and/or significantlyreducing the fiber length and/or the fiber strength, it may be difficultto process and/or may be unsuitable for many downstream applications. Aneed remains for methods of modifying cellulose fiber that may improveboth carboxylic acid and aldehyde functionalities, which methods do notextensively degrade the cellulose fiber. This disclosure provides uniquemethods that resolve one or more of these deficiencies.

Various attempts have been made to oxidize cellulose to provide bothcarboxylic and aldehydic functionality to the cellulose chain withoutdegrading the cellulose fiber. In traditional cellulose oxidationmethods, it may be difficult to control or limit the degradation of thecellulose when aldehyde groups are present on the cellulose. Previousattempts at resolving these issues have included the use of multi-stepoxidation processes, for instance site-specifically modifying certaincarbonyl groups in one step and oxidizing other hydroxyl groups inanother step, and/or providing mediating agents and/or protectingagents, all of which may impart extra cost and by-products to acellulose oxidation process. Thus, there exists a need for methods ofmodifying cellulose that are cost effective and/or can be performed in asingle step of a process, such as a kraft process.

This disclosure provides novel methods that offer vast improvements overmethods attempted in the prior art. Generally, oxidization of cellulosekraft fibers, in the prior art, is conducted after the bleachingprocess. Surprisingly, the inventors have discovered that it is possibleto use the existing stages of a bleaching sequence, particularly thefourth stage of a five stage bleaching sequence, for oxidation ofcellulose fibers. Furthermore, surprisingly, the inventors havediscovered that a metal catalyst, particularly an iron catalyst, couldbe used in the bleaching sequence to accomplish this oxidation withoutinterfering with the final product, for example, because the catalystdid not remain bound in the cellulose resulting in easier removal of atleast some of the residual iron prior to the end of the bleachingsequence than would have been expected based upon the knowledge in theart. Moreover, unexpectedly, the inventors have discovered that suchmethods could be conducted without substantially degrading the fibers.

It is known in the art that cellulose fiber, including kraft pulp, maybe oxidized with metals and peroxides and/or peracids. For instance,cellulose may be oxidized with iron and peroxide (“Fenton's reagent”).See Kishimoto et al., Holzforschung, vol. 52, no. 2 (1998), pp. 180-184.Metals and peroxides, such as Fenton's reagent, are relativelyinexpensive oxidizing agents, making them somewhat desirable for largescale applications, such as kraft processes. In the case of Fenton'sreagent, it is known that this oxidation method can degrade celluloseunder acidic conditions. Thus, it would not have been expected thatFenton's reagent could be used in a kraft process without extensivedegradation of the fibers, for example with an accompanying loss infiber length, at acidic conditions. To prevent degradation of cellulose,Fenton's reagent is often used under alkaline conditions, where theFenton reaction is drastically inhibited. However, additional drawbacksmay exist to using Fenton's reagent under alkaline conditions. Forexample, the cellulose may nonetheless be degraded or discolored. Inkraft pulp processing, the cellulose fiber is often bleached inmulti-stage sequences, which traditionally comprise strongly acidic andstrongly alkaline bleaching steps, including at least one alkaline stepat or near the end of the bleaching sequence. Therefore, contrary towhat was known in the art, it was quite surprising that fiber oxidizedwith iron in an acidic stage of a kraft bleaching process could resultin fiber with enhanced chemical properties, but without physicaldegradation or discoloration.

Thus there is a need for a low cost and/or single step oxidation thatcould impart both aldehyde and carboxylic functionalities to a cellulosefiber, such as a fiber derived from kraft pulp, without extensivelydegrading the cellulose and/or rendering the cellulose unsuitable formany downstream applications. Moreover, there remains a need forimparting high levels of carbonyl groups, such as carboxylic acid,ketone, and aldehyde groups, to cellulose fiber. For example, it wouldbe desirable to use an oxidant under conditions that do not inhibit theoxidation reaction, unlike the use of Fenton's reagent at alkaline pHfor instance, to impart high levels of carbonyl groups. The presentinventors have overcome many difficulties of the prior art, providingmethods that meet these needs.

In addition to the difficulties in controlling the chemical structure ofcellulose oxidation products, and the degradation of those products, itis known that the method of oxidation may affect other properties,including chemical and physical properties and/or impurities in thefinal products. For instance, the method of oxidation may affect thedegree of crystallinity, the hemi-cellulose content, the color, and/orthe levels of impurities in the final product. Ultimately, the method ofoxidation may impact the ability to process the cellulose product forindustrial or other applications.

Bleaching of wood pulp is generally conducted with the aim ofselectively increasing the whiteness or brightness of the pulp,typically by removing lignin and other impurities, without negativelyaffecting physical properties. Bleaching of chemical pulps, such askraft pulps, generally requires several different bleaching stages toachieve a desired brightness with good selectivity. Typically, ableaching sequence employs stages conducted at alternating pH ranges.This alternation aids in the removal of impurities generated in thebleaching sequence, for example, by solubilizing the products of ligninbreakdown. Thus, in general, it is expected that using a series ofacidic stages in a bleaching sequence, such as three acidic stages insequence, would not provide the same brightness as alternatingacidic/alkaline stages, such as acidic-alkaline-acidic. For instance, atypical DEDED sequence produces a brighter product than a DEDAD sequence(where A refers to an acid treatment). Accordingly, a sequence that doesnot have an intervening alkaline stage, yet produces a product withcomparable brightness, would not be expected by a person of skill in theart.

Generally, while it is known that certain bleaching sequences may haveadvantages over others in a kraft process, the reasons behind anyadvantages are less well understood. With respect to oxidation, nostudies have shown any preference for oxidation in a particular stage ofa multi-stage sequence or any recognition that fiber properties can beaffected by post oxidation stages/treatments. For instance, the priorart does not disclose any preference for a later stage oxidation over anearlier stage oxidation. In some embodiments, the disclosure providesmethods uniquely performed in particular stages (e.g., later stages of ableaching process) that have benefits in the kraft process and thatresult in fibers having a unique set of physical and chemicalcharacteristics.

In addition, with respect to brightness in a kraft bleaching process, itis known that metals, in particular transition metals naturally presentin the pulp starting material, are detrimental to the brightness of theproduct. Thus, bleaching sequences frequently aim to remove certaintransition metals from a final product to achieve a target brightness.For example, chelants may be employed to remove naturally occurringmetal from a pulp. Thus, because there is emphasis on removing themetals naturally present in the pulp, a person of skill in the art wouldgenerally not add any metals to a bleaching sequence as that wouldcompound the difficulties in achieving a brighter product.

With respect to iron, moreover, addition of this material to a pulpleads to significant discoloration, akin to the discoloration presentwhen, for example, burning paper. This discoloration, like thediscoloration of burnt paper, has heretofore been believed to benon-reversible. Thus, it has been expected that upon discoloring a woodpulp with added iron, the pulp would suffer a permanent loss inbrightness that could not be recovered with additional bleaching.

Thus, while is known that iron or copper and peroxide can inexpensivelyoxidize cellulose, heretofore they have not been employed in pulpbleaching processes in a manner that achieves a comparable brightness toa standard sequence not employing an iron or copper oxidation step.Generally, their use in pulp bleaching processes has been avoided.Surprisingly, the inventors have overcome these difficulties, and insome embodiments, provide a novel method of inexpensively oxidizingcellulose with iron or copper in a pulp bleaching processes. In someembodiments, the methods disclosed herein result in products that havecharacteristics that are very surprising and contrary to those predictedbased on the teachings of the prior art. Thus, the methods of thedisclosure may provide products that are superior to the products of theprior art and can be more cost-effectively produced.

For instance, it is generally understood in the art that metals, such asiron, bind well to cellulose and cannot be removed by normal washing.Typically, removing iron from cellulose is difficult and costly, andrequires additional processing steps. The presence of high levels ofresidual iron in a cellulose product is known to have several drawbacks,particularly in pulp and papermaking applications. For instance, ironmay lead to discoloration of the final product and/or may be unsuitablefor applications in which the final product is in contact with the skin,such as in diapers and wound dressings. Thus, the use of iron in a kraftbleaching process would be expected to suffer from a number ofdrawbacks.

Heretofore, oxidation treatment of kraft fiber to improve functionalityhas often been limited to oxidation treatment after the fiber wasbleached. Moreover, known processes for rendering a fiber more aldehydicalso cause a concomitant loss in fiber brightness or quality.Furthermore, known processes that result in enhanced aldehydicfunctionality of the fiber also result in a loss of carboxylicfunctionality. The methods of this disclosure do not suffer from one ormore of those drawbacks.

Kraft fiber, produced by a chemical kraft pulping method, provides aninexpensive source of cellulose fiber that generally maintains its fiberlength through pulping, and generally provides final products with goodbrightness and strength characteristics. As such, it is widely used inpaper applications. However, standard kraft fiber has limitedapplicability in downstream applications, such as cellulose derivativeproduction, due to the chemical structure of the cellulose resultingfrom standard kraft pulping and bleaching. In general, standard kraftfiber contains too much residual hemi-cellulose and other naturallyoccurring materials that may interfere with the subsequent physicaland/or chemical modification of the fiber. Moreover, standard kraftfiber has limited chemical functionality, and is generally rigid and nothighly compressible.

The rigid and coarse nature of kraft fiber can require the layering oraddition of different types of materials, such as cotton, inapplications that require contact with human skin, for example, diapers,hygiene products, and tissue products. Accordingly, it may be desirableto provide a cellulose fiber with better flexibility and/or softness toreduce the requirement of using other materials, for example, in amulti-layered product.

Cellulose fiber in applications that involve absorption of bodily wasteand/or fluids, for example, diapers, adult incontinence products, wounddressings, sanitary napkins, and/or tampons, is often exposed to ammoniapresent in bodily waste and/or ammonia generated by bacteria associatedwith bodily waste and/or fluids. It may be desirable in suchapplications to use a cellulose fiber which not only provides bulk andabsorbency, but which also has odor reducing and/or antibacterialproperties, e.g., can reduce odor from nitrogenous compounds, such asammonia (NH₃). Heretofore, modification of kraft fiber by oxidation toimprove its odor control capability invariably came with an undesirabledecrease in brightness. A need exists for an inexpensive modified kraftfiber that exhibits good absorbency characteristics and/or odor controlcapabilities while maintaining good brightness characteristics.

In today's market, consumers desire absorbent products, for example,diapers, adult incontinence products, and sanitary napkins, that arethinner. Ultra-thin product designs require lower fiber weight and cansuffer from a loss of product integrity if the fiber used is too short.Chemical modification of kraft fiber can result in loss of fiber lengthmaking it unacceptable for use in certain types of products, e.g.,ultra-thin products. More specifically, kraft fiber treated to improvealdehyde functionality, which is associated with improved odor control,may suffer from a loss of fiber length during chemical modificationmaking it unsuitable for use in ultra-thin product designs. A needexists for an inexpensive fiber that exhibits compressibility without aloss in fiber length which makes it uniquely suited to ultra-thindesigns (i.e., the product maintains good absorbency based upon theamount of fiber that can be compressed into a smaller space whilemaintaining product integrity at lower fiber weights).

Traditionally, cellulose sources that were useful in the production ofabsorbent products or tissue were not also useful in the production ofdownstream cellulose derivatives, such as cellulose ethers and celluloseesters. The production of low viscosity cellulose derivatives from highviscosity cellulose raw materials, such as standard kraft fiber,required additional manufacturing steps that would add significant costwhile imparting unwanted by-products and reducing the overall quality ofthe cellulose derivative. Cotton linter and high alpha cellulose contentsulfite pulps, which generally have a high degree of polymerization, aregenerally used in the manufacture of cellulose derivatives such ascellulose ethers and esters. However, production of cotton linters andsulfite fiber with a high degree of polymerization and/or viscosity isexpensive due to the cost of the starting material, in the case ofcotton; the high energy, chemical, and environmental costs of pulpingand bleaching, in the case of sulfite pulps; and the extensive purifyingprocesses required, which applies in both cases. In addition to the highcost, there is a dwindling supply of sulfite pulps available to themarket. Therefore, these fibers are very expensive, and have limitedapplicability in pulp and paper applications, for example, where higherDP or higher viscosity pulps may be required. For cellulose derivativemanufacturers these pulps constitute a significant portion of theiroverall manufacturing cost. Thus, there exists a need for low costfibers, such as a modified kraft fiber, that may be used in theproduction of cellulose derivatives.

There is also a need for inexpensive cellulose materials that can beused in the manufacture of microcrystalline cellulose. Microcrystallinecellulose is widely used in food, pharmaceutical, cosmetic, andindustrial applications, and is a purified crystalline form of partiallydepolymerized cellulose. The use of kraft fiber in microcrystallinecellulose production, without the addition of extensive post-bleachingprocessing steps, has heretofore been limited. Microcrystallinecellulose production generally requires a highly purified cellulosicstarting material, which is acid hydrolyzed to remove amorphous segmentsof the cellulose chain. See U.S. Pat. No. 2,978,446 to Battista et al.and U.S. Pat. No. 5,346,589 to Braunstein et al. A low degree ofpolymerization of the chains upon removal of the amorphous segments ofcellulose, termed the “level-off DP,” is frequently a starting point formicrocrystalline cellulose production and its numerical value dependsprimarily on the source and the processing of the cellulose fibers. Thedissolution of the non-crystalline segments from standard kraft fibergenerally degrades the fiber to an extent that renders it unsuitable formost applications because of at least one of 1) remaining impurities; 2)a lack of sufficiently long crystalline segments; or 3) it results in acellulose fiber having too high a degree of polymerization, typically inthe range of 200 to 400, to make it useful in the production ofmicrocrystalline cellulose. Kraft fiber having good purity and/or alower level-off DP value, for example, would be desirable, as the draftfiber may provide greater versatility in microcrystalline celluloseproduction and applications.

In the present disclosure, fiber having one or more of the describedproperties can be produced simply through modification of a typicalkraft pulping plus bleaching process. Fiber of the present disclosureovercomes many of the limitations associated with known modified kraftfiber discussed above.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a chart of final 0.5% capillary CED viscosity as a functionof percent peroxide consumed.

FIG. 2 shows a chart of wet strength to dry strength ratio given as afunction of wet strength resin level.

DESCRIPTION I. Methods

The present disclosure provides novel methods for treating cellulosefiber. In some embodiments, the disclosure provides a method ofmodifying cellulose fiber, comprising providing cellulose fiber, andoxidizing the cellulose fiber. As used herein, “oxidized,”“catalytically oxidized,” “catalytic oxidation” and “oxidation” are allunderstood to be interchangeable and refer to treatment of cellulosefiber with at least a catalytic amount of at least one of iron or copperand at least one peroxide, such as hydrogen peroxide, such that at leastsome of the hydroxyl groups of the cellulose fibers are oxidized. Thephrase “iron or copper” and similarly “iron (or copper)” mean “iron orcopper or a combination thereof.” In some embodiments, the oxidationcomprises simultaneously increasing carboxylic acid and aldehyde contentof the cellulose fiber.

The cellulose fiber used in the methods described herein may be derivedfrom softwood fiber, hardwood fiber, and mixtures thereof. In someembodiments, the modified cellulose fiber is derived from softwood, suchas southern pine. In some embodiments, the modified cellulose fiber isderived from hardwood, such as eucalyptus. In some embodiments, themodified cellulose fiber is derived from a mixture of softwood andhardwood. In yet another embodiment, the modified cellulose fiber isderived from cellulose fiber that has previously been subjected to allor part of a kraft process, i.e., kraft fiber.

References in this disclosure to “cellulose fiber” or “kraft fiber” areinterchangeable except where specifically indicated as different or asone of ordinary skill in the art would understand them to be different.

In at least one embodiment, the method comprises providing cellulosefiber, and oxidizing the cellulose fiber while generally maintaining thefiber length of the cellulose fibers.

“Fiber length” and “average fiber length” are used interchangeably whenused to describe the property of a fiber and mean the length-weightedaverage fiber length. Therefore, for example, a fiber having an averagefiber length of 2 mm should be understood to mean a fiber having alength-weighted average fiber length of 2 mm.

In at least one embodiment, the method comprises providing cellulosefiber, partially bleaching the cellulose fiber, and oxidizing thecellulose fiber. In some embodiments, the oxidation is conducted in thebleaching process. In some embodiments, the oxidation is conducted afterthe bleaching process.

In at least one embodiment, the method comprises providing the cellulosefiber, and oxidizing cellulose fiber thereby reducing the degree ofpolymerization of the cellulose fiber.

In at least one embodiment, the method comprises providing cellulosefiber, and oxidizing the cellulose fiber while maintaining the CanadianStandard Freeness (“freeness”) of that cellulose fiber.

In at least one embodiment, the method comprises providing cellulosefiber, oxidizing the cellulose fiber, and increasing the brightness ofthat oxidized cellulose fiber over standard cellulose fiber.

As discussed above, in accordance with the disclosure, oxidation ofcellulose fiber involves treating the cellulose fiber with at least acatalytic amount of iron or copper and hydrogen peroxide. In at leastone embodiment, the method comprises oxidizing cellulose fiber with ironand hydrogen peroxide. The source of iron can be any suitable source, asa person of skill would recognize, such as for example ferrous sulfate(for example ferrous sulfate heptahydrate), ferrous chloride, ferrousammonium sulfate, ferric chloride, ferric ammonium sulfate, or ferricammonium citrate.

In some embodiments, the method comprises oxidizing the cellulose fiberwith copper and hydrogen peroxide. Similarly, the source of copper canbe any suitable source as a person of skill would recognize. Finally, insome embodiments, the method comprises oxidizing the cellulose fiberwith a combination of copper and iron and hydrogen peroxide.

In some embodiments, the disclosure provides a method for treatingcellulose fiber, comprising, providing cellulose fiber, pulping thecellulose fiber, bleaching the cellulose fiber, and oxidizing thecellulose fiber.

In some embodiments, the method further comprises oxygen delignifyingthe cellulose fiber. Oxygen delignification can be performed by anymethod known to those of ordinary skill in the art. For instance, oxygendelignification may be a conventional two-stage oxygen delignification.It is known, for example, that oxygen delignifying cellulose fiber, suchas kraft fiber, may alter the carboxylic acid and/or aldehyde content ofthe cellulose fiber during processing. In some embodiments, the methodcomprises oxygen delignifying the cellulose fiber before bleaching thecellulose fiber.

In at least one embodiment, the method comprises oxidizing cellulosefiber in at least one of a kraft pulping step, an oxygen delignificationstep, and a kraft bleaching step. In a preferred embodiment, the methodcomprises oxidizing the cellulose fiber in at least one kraft bleachingstep. In at least one embodiment, the method comprises oxidizing thecellulose fiber in two or more than one kraft bleaching steps.

When cellulose fiber is oxidized in a bleaching step, cellulose fibershould not be subjected to substantially alkaline conditions in thebleaching process during or after the oxidation. In some embodiments,the method comprises oxidizing cellulose fiber at an acidic pH. In someembodiments, the method comprises providing cellulose fiber, acidifyingthe cellulose fiber, and then oxidizing the cellulose fiber at acidicpH. In some embodiments, the pH ranges from about 2 to about 6, forexample from about 2 to about 5 or from about 2 to about 4.

The pH can be adjusted using any suitable acid, as a person of skillwould recognize, for example, sulfuric acid or hydrochloric acid orfiltrate from an acidic bleach stage of a bleaching process, such as achlorine dioxide (D) stage of a multi-stage bleaching process. Forexample, the cellulose fiber may be acidified by adding an extraneousacid. Examples of extraneous acids are known in the art and include, butare not limited to, sulfuric acid, hydrochloric acid, and carbonic acid.In some embodiments, the cellulose fiber is acidified with acidicfiltrate, such as waste filtrate, from a bleaching step. In someembodiments, the acidic filtrate from a bleaching step does not have ahigh iron content. In at least one embodiment, the cellulose fiber isacidified with acidic filtrate from a D stage of a multi-stage bleachingprocess.

In some embodiments, the method comprises oxidizing the cellulose fiberin one or more stages of a multi-stage bleaching sequence. In someembodiments, the method comprises oxidizing the cellulose fiber in asingle stage of a multi-stage bleaching sequence. In some embodiments,the method comprises oxidizing the cellulose fiber at or near the end ofa multi-stage bleaching sequence. In some embodiments, the methodcomprises oxidizing cellulose fiber in at least the fourth stage of afive-stage bleaching sequence.

In accordance with the disclosure, the multi-stage bleaching sequencecan be any bleaching sequence that does not comprise an alkalinebleaching step following the oxidation step. In at least one embodiment,the multi-stage bleaching sequence is a five-stage bleaching sequence.In some embodiments, the bleaching sequence is a DEDED sequence. In someembodiments, the bleaching sequence is a D₀E1D1E2D2 sequence. In someembodiments, the bleaching sequence is a D₀(EoP)D1E2D2 sequence. In someembodiments the bleaching sequence is a D₀(EO)D1E2D2.

The non-oxidation stages of a multi-stage bleaching sequence may includeany convention or after discovered series of stages, be conducted underconventional conditions, with the proviso that to be useful in producingthe modified fiber described in the present disclosure, no alkalinebleaching step may follow the oxidation step.

In some embodiments, the oxidation is incorporated into the fourth stageof a multi-stage bleaching process. In some embodiments, the method isimplemented in a five-stage bleaching process having a sequence ofD₀E1D1E2D2, and the fourth stage (E2) is used for oxidizing kraft fiber.

In some embodiments, the kappa number increases after oxidation of thecellulose fiber. More specifically, one would typically expect adecrease in kappa number across this bleaching stage based upon theanticipated decrease in material, such as lignin, which reacts with thepermanganate reagent. However, in the method as described herein, thekappa number of cellulose fiber may decrease because of the loss ofimpurities, e.g., lignin; however, the kappa number may increase becauseof the chemical modification of the fiber. Not wishing to be bound bytheory, it is believed that the increased functionality of the modifiedcellulose provides additional sites that can react with the permanganatereagent. Accordingly, the kappa number of modified kraft fiber iselevated relative to the kappa number of standard kraft fiber.

In at least one embodiment, the oxidation occurs in a single stage of ableaching sequence after both the iron or copper and peroxide have beenadded and some retention time provided. An appropriate retention is anamount of time that is sufficient to catalyze the hydrogen peroxide withthe iron or copper. Such time will be easily ascertainable by a personof ordinary skill in the art.

In accordance with the disclosure, the oxidation is carried out for atime and at a temperature that is sufficient to produce the desiredcompletion of the reaction. For example, the oxidation may be carriedout at a temperature ranging from about 60 to about 80 degrees C., andfor a time ranging from about 40 to about 80 minutes. The desired timeand temperature of the oxidation reaction will be readily ascertainableby a person of skill in the art.

Advantageously, the cellulose fiber is digested to a target kappa numberbefore bleaching. For example, when the oxidized cellulose is desiredfor paper grade or fluff pulp cellulose, the cellulose fiber may bedigested in a two-vessel hydraulic digester with Lo-Solids™ cooking to akappa number ranging from about 30 to about 32 before bleaching andoxidizing the cellulose. Alternatively, if oxidized cellulose is desiredfor cellulose derivative applications, for instance in the manufactureof cellulose ethers, cellulose fiber may be digested to a kappa numberranging from about 20 to about 24 before bleaching and oxidizing thecellulose according to the methods of this disclosure. In someembodiments, the cellulose fiber is digested and delignified in aconventional two-stage oxygen delignification step before bleaching andoxidizing the cellulose fiber. Advantageously, the delignification iscarried out to a target kappa number ranging from about 6 to about 8when the oxidized cellulose is intended for cellulose derivativeapplications, and a target kappa number ranging from about 12 to about14 when the oxidized cellulose is intended for paper and/or fluffapplications.

In some embodiments, the bleaching process is conducted under conditionsto target about 88-90% final ISO brightness, such as ranging from about85 to about 95%, or from about 88% to about 90%.

The disclosure also provides a method of treating cellulose fiber,comprising providing cellulose fiber, reducing the DP of the cellulosefiber, and maintaining the fiber length of the cellulose fiber. In someembodiments, the cellulose fiber is kraft fiber. In some embodiments,the DP of the cellulose fiber is reduced in a bleaching process. In someembodiments, the DP of the cellulose fiber is reduced at or near the endof a multi-stage bleaching sequence. In some embodiments, the DP isreduced in at least the fourth stage of a multi-stage bleachingsequence. In some embodiments, the DP is reduced in or after the fourthstage of a multi-stage bleaching sequence.

Alternatively, the multi-stage bleaching sequence may be altered toprovide more robust bleaching conditions prior to oxidizing thecellulose fiber. In some embodiments, the method comprises providingmore robust bleaching conditions prior to the oxidation step. Morerobust bleaching conditions may allow the degree of polymerizationand/or viscosity of the cellulose fiber to be reduced in the oxidationstep with lesser amounts of iron or copper and/or hydrogen peroxide.Thus, it may be possible to modify the bleaching sequence conditions sothat the brightness and/or viscosity of the final cellulose product canbe further controlled. For instance, reducing the amounts of peroxideand metal, while providing more robust bleaching conditions beforeoxidation, may provide a product with lower viscosity and higherbrightness than an oxidized product produced with identical oxidationconditions but with less robust bleaching. Such conditions may beadvantageous in some embodiments, particularly in cellulose etherapplications.

In some embodiments, the methods of the disclosure further comprisereducing the crystallinity of cellulose fiber so that it is lower thanthe crystallinity of that celluolose fiber as measured before theoxidation stage. For example, in accordance with the methods of thedisclosure, the crystallinity index of the cellulose fiber may bereduced up to 20% relative to the starting crystallinity index asmeasured before the oxidation stage.

In some embodiments, the methods of the disclosure further comprisetreating the modified cellulose fiber with at least one caustic oralkaline substance. For example, in at least one embodiment, a method oftreating cellulose fiber comprises providing an oxidized cellulose fiberof the disclosure, exposing the oxidized cellulose fiber to an alkalineor caustic substance, and then dry laying the cellulose product. Withoutbeing bound by theory, it is believed that the addition of at least onecaustic substance to the modified cellulose may result in a cellulosefiber having very high functionality and very low fiber length.

It is known that cellulose comprising increased aldehyde groups may haveadvantageous properties in improving the wet strength of cellulosefibers. See, For Example, U.S. Pat. No. 6,319,361 to Smith et al., andU.S. Pat. No. 6,582,559 to Thornton et al. Such properties may bebeneficial, for example, in absorbent material applications. In someembodiments, the disclosure provides a method for improving the wetstrength of a product, comprising providing modified cellulose fiber ofthe disclosure and adding the modified cellulose fiber of the disclosureto a product, such as a paper product. For example, the method maycomprise oxidizing cellulose fiber in a bleaching process, furthertreating the oxidized cellulose fiber with an acidic or causticsubstance, and adding the treated fiber to a cellulose product.

In accordance with the disclosure, hydrogen peroxide is added to thecellulose fiber in acidic media in an amount sufficient to achieve thedesired oxidation and/or degree of polymerization and/or viscosity ofthe final cellulose product. For example, peroxide can be added in anamount of from about 0.1 to about 4%, or from about 1% to about 3%, orfrom about 1% to about 2%, or from about 2% to about 3%, based on thedry weight of the pulp.

Iron or copper are added at least in an amount sufficient to catalyzethe oxidation of the cellulose with peroxide. For example, iron can beadded in an amount ranging from about 25 to about 200 ppm based on thedry weight of the kraft pulp. A person of skill in the art will be ableto readily optimize the amount of iron or copper to achieve the desiredlevel or amount of oxidation and/or degree of polymerization and/orviscosity of the final cellulose product.

In some embodiments, the method further involves adding steam eitherbefore or after the addition of hydrogen peroxide.

In some embodiments, the final DP and/or viscosity of the pulp can becontrolled by the amount of iron or copper and hydrogen peroxide and therobustness of the bleaching conditions prior to the oxidation step. Aperson of skill in the art will recognize that other properties of themodified kraft fiber of the disclosure may be affected by the amounts ofiron or copper and hydrogen peroxide and the robustness of the bleachingconditions prior to the oxidation step. For example, a person of skillin the art may adjust the amounts of iron or copper and hydrogenperoxide and the robustness of the bleaching conditions prior to theoxidation step to target or achieve a desired brightness in the finalproduct and/or a desired degree of polymerization or viscosity.

In some embodiments, the disclosure provides a method of modifyingcellulose fiber, comprising providing cellulose fiber, reducing thedegree of polymerization of the cellulose fiber, and maintaining thefiber length of the cellulose fiber.

In some embodiments, the oxidized kraft fiber of the disclosure is notrefined. Refining of the oxidized kraft fiber may have a negative impacton its fiber length and integrity, for instance refining the fiber maycause the fiber to fall apart.

In some embodiments, each stage of the five-stage bleaching processincludes at least a mixer, a reactor, and a washer (as is known to thoseof skill in the art).

In some embodiments, a kraft pulp is acidified on a D1 stage washer, theiron source is also added to the kraft pulp on the D1 stage washer, theperoxide is added following the iron source (or copper source) at anaddition point in the mixer or pump before the E2 stage tower, the kraftpulp is reacted in the E2 tower and washed on the E2 washer, and steammay optionally be added before the E2 tower in a steam mixer.

In some embodiments, iron (or copper) can be added up until the end ofthe D1 stage, or the iron (or copper) can also be added at the beginningof the E2 stage, provided that the pulp is acidified first (i.e., priorto addition of the iron) at the D1 stage. Steam may be optionally addedeither before or after the addition of the peroxide.

In an exemplary embodiment, the method for preparing a low viscositymodified cellulose fiber may involve bleaching kraft pulp in amulti-stage bleaching process and reducing the DP of the pulp at or neara final stage of the multi-stage bleaching process (for example in the4th stage of a multi-stage bleaching process, for example in the 4thstage of a 5 stage bleaching process) using a treatment with hydrogenperoxide in an acidic media and in the presence of iron. For instance,the final DP of the pulp may be controlled by the appropriateapplication of the iron or copper and hydrogen peroxide, as furtherdescribed in the Examples section. In some embodiments, the iron orcopper and hydrogen peroxide is provided in amounts and under conditionsappropriate for producing a low DP fiber (i.e., a fiber having a DPwranging from about 1180 to about 1830, or a 0.5% Capillary CED viscosityranging from about 7 to about 13 mPa·s). In some exemplary embodiments,the iron or copper and hydrogen peroxide may be provided in amounts andunder conditions appropriate for producing an ultra low DP fiber (i.e.,a fiber having a DPw ranging from about 700 to about 1180, or a 0.5%0.5% Capillary CED viscosity ranging from about 3.0 to about 7 mPa·s).

For example, in some embodiments, the treatment with hydrogen peroxidein an acidic media with iron or copper may involve adjusting the pH ofthe kraft pulp to a pH ranging from about 2 to about 5, adding a sourceof iron to the acidified pulp, and adding hydrogen peroxide to the kraftpulp.

In some embodiments, for example, the method of preparing a modifiedcellulose fiber within the scope of the disclosure may involveacidifying the kraft pulp to a pH ranging from about 2 to about 5 (usingfor example sulfuric acid), mixing a source of iron (for example ferroussulfate, for example ferrous sulfate heptahydrate) with the acidifiedkraft pulp at an application of from about 25 to about 250 ppm Fe⁺²based on the dry weight of the kraft pulp at a consistency ranging fromabout 1% to about 15% and also hydrogen peroxide, which can be added asa solution at a concentration of from about 1% to about 50% by weightand in an amount ranging from about 0.1% to about 1.5% based on the dryweight of the kraft pulp. In some embodiments, the ferrous sulfatesolution is mixed with the kraft pulp at a consistency ranging fromabout 7% to about 15%. In some embodiments the acidic kraft pulp ismixed with the iron source and reacted with the hydrogen peroxide for atime period ranging from about 40 to about 80 minutes at a temperatureranging from about 60 to about 80 degrees C.

In some embodiments, the method of preparing a modified cellulose fiberwithin the scope of this disclosure involves reducing DP by treating akraft pulp with hydrogen peroxide in an acidic media in the presence ofiron (or copper), wherein the acidic, hydrogen peroxide and iron (orcopper) treatment is incorporated into a multi-stage bleaching process.In some embodiments, the treatment with iron, acid and hydrogen peroxideis incorporated into a single stage of the multi-stage bleachingprocess. In some embodiments, the treatment with iron (or copper), acidand hydrogen peroxide is incorporated into a single stage that is at ornear the end of the multi-stage bleaching process. In some embodiments,the treatment with iron (or copper), acid and hydrogen peroxide isincorporated into the fourth stage of a multi-stage bleaching process.For example, the pulp treatment may occur in a single stage, such as theE2 stage, after both the iron (or copper) and peroxide have been addedand some retention time provided. In some embodiments, each stage of afive stage bleaching process includes at least a mixer, a reactor, and awasher (as is known to those of skill in the art), and the kraft pulpmay be acidified on the D1 stage washer, the iron source may also beadded to the kraft pulp on the D1 stage washer, the peroxide may beadded following the iron source (or copper source) at an addition pointin the mixer or pump before the E2 stage tower, the kraft pulp may bereacted in the E2 tower and washed on the E2 washer, and steam mayoptionally be added before the E2 tower in a steam mixer. In someembodiments, for example, iron (or copper) can be added up until the endof the D1 stage, or the iron (or copper) could also be added at thebeginning of the E2 stage, provided that the pulp is acidified first(i.e., prior to addition of the iron) at the D1 stage, extra acid may beadded if needed to bring the pH into the range of from about 3 to about5, and peroxide may be added after the iron (or copper). Steam may beadded either before or after the addition of the peroxide.

For example, in one embodiment, the above-described five stage bleachingprocesses conducted with a softwood cellulose starting material mayproduce modified cellulose fiber having one or more of the followingproperties: an average fiber length of at least 2.2 mm, a viscosityranging from about 3.0 mPa·s to less than 13 mPa·s, an S10 causticsolubility ranging from about 16% to about 20%, an S18 causticsolubility ranging from about 14% to about 18%, a carboxyl contentranging from about 2 meq/100 g to about 6 meq/100 g, an aldehyde contentranging from about 1 meq/100 g to about 3 meq/100 g, a carbonyl contentof from about 1 to 4, a freeness ranging from about 700 mls to about 760mls, a fiber strength ranging from about 5 km to about 8 km, and abrightness ranging from about 85 to about 95 ISO. For example, in someembodiments, the above-described exemplary five stage bleachingprocesses may produce modified cellulose softwood fibers having each ofthe afore-mentioned properties.

According to another example, wherein the cellulose fiber is a softwoodfiber, the above-described exemplary five stage bleaching processes mayproduce a modified cellulose softwood fiber having an average fiberlength that is at least 2.0 mm (for example ranging from about 2.0 mm toabout 3.7 mm, or from about 2.2 mm to about 3.7 mm), a viscosity that isless than 13 mPa·s (for example a viscosity ranging from about 3.0 mPa·sto less than 13 mPa·s, or from about 3.0 mPa·s to about 5.5 mPa·s, orfrom about 3.0 mPa·s to about 7 mPa·s, or from about 7 mPa·s to lessthan 13 mPa·s), and a brightness of at least 85 (for example rangingfrom about 85 to about 95).

In some embodiments, the disclosure provides a method for producingfluff pulp, comprising providing modified kraft fiber of the disclosureand then producing a fluff pulp. For example, the method comprisesbleaching kraft fiber in a multi-stage bleaching process, oxidizing thefiber in at least the fourth or fifth stage of the multi-stage bleachingprocess with hydrogen peroxide under acidic conditions and a catalyticamount of iron or copper, and then forming a fluff pulp. In at least oneembodiment, the fiber is not refined after the multi-stage bleachingprocess.

The disclosure also provides a method for reducing odor, such as odorfrom bodily waste, for example odor from urine or blood. In someembodiments, the disclosure provides a method for controlling odor,comprising providing a modified bleached kraft fiber according to thedisclosure, and applying an odorant to the bleached kraft fiber suchthat the atmospheric amount of odorant is reduced in comparison with theatmospheric amount of odorant upon application of an equivalent amountof odorant to an equivalent weight of standard kraft fiber. In someembodiments the disclosure provides a method for controlling odorcomprising inhibiting bacterial odor generation. In some embodiments,the disclosure provides a method for controlling odor comprisingabsorbing odorants, such as nitrogenous odorants, onto a modified kraftfiber. As used herein, “nitrogenous odorants” is understood to meanodorants comprising at least one nitrogen.

In at least one embodiment, a method of reducing odor comprisesproviding modified cellulose fiber according to the disclosure, andapplying an odorant, such as a nitrogenous compound, for instanceammonia, or an organism that is capable of generating a nitrogenouscompound to the modified kraft fiber. In some embodiments, the methodfurther comprises forming a fluff pulp from modified cellulose fiberbefore adding an odorant to the modified kraft fiber. In someembodiments, the odorant comprises at least one bacteria capable ofproducing nitrogenous compounds. In some embodiments, the odorantcomprises nitrogenous compounds, such as ammonia.

In some embodiments, the method of reducing odor further comprisesabsorbing ammonia onto modified cellulose fiber. In some embodiments,the method of reducing odor further comprises inhibiting bacterialammonia production. In some embodiments, the method of inhibitingbacterial ammonia production comprises inhibiting bacterial growth. Insome embodiments, the method of inhibiting bacterial ammonia productioncomprises inhibiting bacterial urea synthesis.

In some embodiments, a method of reducing odor comprises combiningmodified cellulose fiber with at least one other odor reductant, andthen applying an odorant to the modified cellulose fiber combined withodor reductant.

Exemplary odor reductants are known in the art, and include, forexample, odor reducing agents, odor masking agents, biocides, enzymes,and urease inhibitors. For instance, modified cellulose fiber may becombined with at least one odor reductant chosen from zeolites,activated carbons, diatomaceous earth, cyclodextrins, clay, chelatingagents, such as those containing metal ions, such as copper, silver orzinc ions, ion exchange resins, antibacterial or antimicrobial polymers,and/or aromatizers.

In some embodiments, the modified cellulose fiber is combined with atleast one super absorbent polymer (SAP). In some embodiments, the SAPmay by an odor reductant. Examples of SAP that can be used in accordancewith the disclosure include, but are not limited to, Hysorb™ sold by thecompany BASF, Aqua Keep® sold by the company Sumitomo, and FAVOR®, soldby the company Evonik.

II. Kraft Fibers

Reference is made herein to “standard,” “conventional,” or“traditional,” kraft fiber, kraft bleached fiber, kraft pulp or kraftbleached pulp. Such fiber or pulp is often described as a referencepoint for defining the improved properties of the present invention. Asused herein, these terms are interchangeable and refer to the fiber orpulp which is identical in composition to and processed in a like mannerto the target fiber or pulp without having been subject to anyoxidation, either alone or followed by one or more of alkaline or acidtreatments (i.e., processed in the standard or conventional manner). Asused herein, the term “modified” refers to fiber that has been subjectto an oxidation treatment, either alone or followed by one or more ofalkaline or acid treatments.

Physical characteristics (for example, fiber length and viscosity) ofthe modified cellulose fiber mentioned in the specification are measuredin accordance with protocols provided in the Examples section.

The present disclosure provides kraft fiber with low and ultra-lowviscosity. Unless otherwise specified, “viscosity” as used herein refersto 0.5% Capillary CED viscosity measured according to TAPPI T230-om99 asreferenced in the protocols. Modified kraft fiber of the presentinvention exhibits unique characteristics which are indicative of thechemical modifications that have been made to it. More specifically,fiber of the present invention exhibits characteristics similar to thoseof standard kraft fiber, i.e., length and freeness, but also exhibitssome very different characteristics which are a function of theincreased number of functional groups that are included in the modifiedfiber. This modified fiber exhibits unique characteristics whensubjected to the cited TAPPI test for measuring viscosity. Specifically,the cited TAPPI test treats fiber with a caustic agent as part of thetest method. The application of caustic to the modified fiber, asdescribed, causes the modified fiber to hydrolyze differently thanstandard kraft fiber thus reporting a viscosity which is generally lowerthan the viscosity of standard kraft fiber. Accordingly, a person ofskill in the art will understand that the reported viscosities may beaffected by the viscosity measurement method. For purposes of thepresent invention, the viscosities reported herein as measured by thecited TAPPI method represent the viscosity of the kraft fiber used tocalculate the degree of polymerization of the fiber.

Unless otherwise specified, “DP” as used herein refers to average degreeof polymerization by weight (DPw) calculated from 0.5% Capillary CEDviscosity measured according to TAPPI T230-om99. See, e.g., J. F.Cellucon Conference in The Chemistry and Processing of Wood and PlantFibrous Materials, p. 155, test protocol 8, 1994 (Woodhead PublishingLtd., Abington Hall, Abinton Cambridge CBI 6AH England, J. F. Kennedy etal. eds.) “Low DP” means a DP ranging from about 1160 to about 1860 or aviscosity ranging from about 7 to about 13 mPa·s. “Ultra low DP” fibersmeans a DP ranging from about 350 to about 1160 or a viscosity rangingfrom about 3 to about 7 mPa·s.

In some embodiments, modified cellulose fiber has a DP ranging fromabout 350 to about 1860. In some embodiments, the DP ranges from about710 to about 1860. In some embodiments, the DP ranges from about 350 toabout 910. In some embodiments, the DP ranges from about 350 to about1160. In some embodiments, the DP ranges from about 1160 to about 1860.In some embodiments, the DP is less than 1860, less than 1550, less than1300, less than 820, or less than 600.

In some embodiments, modified cellulose fiber has a viscosity rangingfrom about 3.0 mPa·s to about 13 mPa·s. In some embodiments, theviscosity ranges from about 4.5 mPa·s to about 13 mPa·s. In someembodiments, the viscosity ranges from about 3.0 mPa·s to about 5.5mPa·s. In some embodiments, the viscosity ranges from about 3.0 mPa·s toabout 7 mPa·s. In some embodiments, the viscosity ranges from about 7mPa·s to about 13 mPa·s. In some embodiments, the viscosity is less than13 mPa·s, less than 10 mPa·s, less than 8 mPa·s, less than 5 mPa·s, orless than 4 mPa·s.

In some embodiments, the modified kraft fiber of the disclosuremaintains its freeness during the bleaching process. In someembodiments, the modified cellulose fiber has a “freeness” of at leastabout 690 mls, such as at least about 700 mls, or about 710 mls, orabout 720 mls, or about 730 mls.

In some embodiments, modified kraft fiber of the disclosure maintainsits fiber length during the bleaching process.

In some embodiments, when the modified cellulose fiber is a softwoodfiber, the modified cellulose fiber has an average fiber length, asmeasured in accordance with Test Protocol 12, described in the Examplesection below, that is about 2 mm or greater. In some embodiments, theaverage fiber length is no more than about 3.7 mm. In some embodiments,the average fiber length is at least about 2.2 mm, about 2.3 mm, about2.4 mm, about 2.5 mm, about 2.6 mm, about 2.7 mm, about 2.8 mm, about2.9 mm, about 3.0 mm, about 3.1 mm, about 3.2 mm, about 3.3 mm, about3.4 mm, about 3.5 mm, about 3.6 mm, or about 3.7 mm. In someembodiments, the average fiber length ranges from about 2 mm to about3.7 mm, or from about 2.2 mm to about 3.7 mm.

In some embodiments, when the modified cellulose fiber is a hardwoodfiber, the modified cellulose fiber has an average fiber length fromabout 0.75 to about 1.25 mm. For example, the average fiber length maybe at least about 0.85 mm, such as about 0.95 mm, or about 1.05 mm, orabout 1.15 mm.

In some embodiments, modified kraft fiber of the disclosure has abrightness equivalent to kraft fiber standard kraft fiber. In someembodiments, the modified cellulose fiber has a brightness of at least85, 86, 87, 88, 89, or 90 ISO. In some embodiments, the brightness is nomore than about 92. In some embodiments, the brightness ranges fromabout 85 to about 92, or from about 86 to about 90, or from about 87 toabout 90, or from about 88 to about 90.

In some embodiments, modified cellulose fiber of the disclosure is morecompressible and/or embossable than standard kraft fiber. In someembodiments, modified cellulose fiber may be used to produce structuresthat are thinner and/or have higher density than structures producedwith equivalent amounts of standard kraft fiber.

In some embodiments, modified cellulose fiber of the disclosure may becompressed to a density of at least about 0.21 g/cc, for example about0.22 g/cc, or about 0.23 g/cc, or about 0.24 g/cc. In some embodiments,modified cellulose fiber of the disclosure may be compressed to adensity ranging from about 0.21 to about 0.24 g/cc. In at least oneembodiment, modified cellulose fiber of the disclosure, upon compressionat 20 psi gauge pressure, has a density ranging from about 0.21 to about0.24 g/cc.

In some embodiments, modified cellulose fiber of the disclosure, uponcompression under a gauge pressure of about 5 psi, has a density rangingfrom about 0.110 to about 0.114 g/cc. For example, modified cellulosefiber of the disclosure, upon compression under a gauge pressure ofabout 5 psi, may have a density of at least about 0.110 g/cc, forexample at least about 0.112 g/cc, or about 0.113 g/cc, or about 0.114g/cc.

In some embodiments, modified cellulose fiber of the disclosure, uponcompression under a gauge pressure of about 10 psi, has a densityranging from about 0.130 to about 0.155 g/cc. For example, the modifiedcellulose fiber of the disclosure, upon compression under a gaugepressure of about 10 psi, may have a density of at least about 0.130g/cc, for example at least about 0.135 g/cc, or about 0.140 g/cc, orabout 0.145 g/cc, or about 0.150 g/cc.

In some embodiments, modified cellulose fiber of the disclosure can becompressed to a density of at least about 8% higher than the density ofstandard kraft fiber. In some embodiments, the modified cellulose fiberof the disclosure have a density of about 8% to about 16% higher thanthe density of standard kraft fiber, for example from about 10% to about16% higher, or from about 12% to about 16% higher, or from about 13% toabout 16% higher, or from about 14% to about 16% higher, or from about15% to about 16% higher.

In some embodiments, modified kraft fiber of the disclosure hasincreased carboxyl content relative to standard kraft fiber.

In some embodiments, modified cellulose fiber has a carboxyl contentranging from about 2 meq/100 g to about 9 meq/100 g. In someembodiments, the carboxyl content ranges from about 3 meq/100 g to about8 meq/100 g. In some embodiments, the carboxyl content is about 4meq/100 g. In some embodiments, the carboxyl content is at least about 2meq/100 g, for example, at least about 2.5 meq/100 g, for example, atleast about 3.0 meq/100 g, for example, at least about 3.5 meq/100 g,for example, at least about 4.0 meq/100 g, for example, at least about4.5 meq/100 g, or for example, at least about 5.0 meq/100 g.

Modified kraft fiber of the disclosure has increased aldehyde contentrelative to standard bleached kraft fiber. In some embodiments, themodified kraft fiber has an aldehyde content ranging from about 1meq/100 g to about 9 meq/100 g. In some embodiments, the aldehydecontent is at least about 1.5 meq/100 g, about 2 meq/100 g, about 2.5meq/100 g, about 3.0 meq/100 g, about 3.5 meq/100 g, about 4.0 meq/100g, about 4.5 meq/100 g, or about 5.0 meq/100 g, or at least about 6.5meq, or at least about 7.0 meq.

In some embodiments, the modified cellulose fiber has a ratio of totalaldehyde to carboxyl content of greater than about 0.3, such as greaterthan about 0.5, such as greater than about 1, such as greater than about1.4. In some embodiments, the aldehyde to carboxyl ratio ranges fromabout 0.3 to about 1.5. In some embodiments, the ratio ranges from about0.3 to about 0.5. In some embodiments, the ratio ranges from about 0.5to about 1. In some embodiments, the ratio ranges from about 1 to about1.5.

In some embodiments, modified kraft fiber has higher kink and curl thanstandard kraft fiber. Modified kraft fiber according to the presentinvention has a kink index in the range of about 1.3 to about 2.3. Forinstance, the kink index may range from about 1.5 to about 2.3, or fromabout 1.7 to about 2.3 or from about 1.8 to about 2.3, or from about 2.0to about 2.3. Modified kraft fiber according to the present disclosuremay have a length weighted curl index in the range of about 0.11 toabout 0.23, such as from about 0.15 to about 0.2.

In some embodiments, the crystallinity index of modified kraft fiber isreduced from about 5% to about 20% relative to the crystallinity indexof standard kraft fiber, for instance from about 10% to about 20%, orfrom about 15% to about 20%.

In some embodiments, modified cellulose according to the presentdisclosure has an R10 value ranging from about 65% to about 85%, forinstance from about 70% to about 85%, or from about 75% to about 85%. Insome embodiments, modified fiber according to the disclosure has an R18value ranging from about 75% to about 90%, for instance from about 80%to about 90%, for example from about 80% to about 87%. The R18 and R10content is described in TAPPI 235. R10 represents the residualundissolved material that is left extraction of the pulp with 10 percentby weight caustic and R18 represents the residual amount of undissolvedmaterial left after extraction of the pulp with an 18% caustic solution.Generally, in a 10% caustic solution, hemicellulose and chemicallydegraded short chain cellulose are dissolved and removed in solution. Incontrast, generally only hemicellulose is dissolved and removed in an18% caustic solution. Thus, the difference between the R10 value and theR18 value, (R=R18−R10), represents the amount of chemically degradedshort chained cellulose that is present in the pulp sample.

Based on one or more of the above-cited properties, such as the kink andcurl of the fiber, the increased functionality, and the crystallinity ofthe modified kraft fiber, a person of skill in the art would expect themodified kraft fiber of the disclosure to have certain characteristicsthat standard kraft fiber does not possess. For instance, it is believedthat kraft fiber of the disclosure may be more flexible than standardkraft fiber, and may elongate and/or bend and/or exhibit elasticityand/or increase wicking. Moreover, without being bound by theory, it isexpected that modified kraft fiber may provide a physical structure, forexample in a fluff pulp, that would either cause fiber entanglement andfiber/fiber bonding or would entangle materials applied to the pulp,such that they these materials remain in a relatively fixed spatialposition within the pulp, retarding their dispersion. Additionally, itis expected, at least because of the reduced crystallinity relative tostandard kraft fiber, that modified kraft fiber of the disclosure wouldbe softer than standard kraft fiber, enhancing their applicability inabsorbent product applications, for example, such as diaper and bandageapplications.

In some embodiments, modified cellulose fiber has an S10 causticsolubility ranging from about 16% to about 30%, or from about 14% toabout 16%. In some embodiments, modified cellulose fiber has an S18caustic solubility ranging from about 14% to about 22%, or from about14% to about 16%. In some embodiments, modified cellulose fiber has a ΔR(difference between S10 and S18) of about 2.9 or greater. In someembodiments the ΔR is about 6.0 or greater.

In some embodiments, modified cellulose fiber strength, as measured bywet zero span breaking length, ranges from about 4 km to about 10 km,for instance, from about 5 km to about 8 km. In some embodiments, thefiber strength is at least about 4 km, about 5 km, about 6 km, about 7km, or about 8 km. In some embodiments, the fiber strength ranges fromabout 5 km to about 7 km, or from about 6 km to about 7 km.

In some embodiments, modified kraft fiber has odor control properties.In some embodiments, modified kraft fiber is capable of reducing theodor of bodily waste, such as urine or menses. In some embodimentsmodified kraft fiber absorbs ammonia. In some embodiments, modifiedkraft fiber inhibits bacterial odor production, for example, in someembodiments, modified kraft fiber inhibits bacterial ammonia production.

In at least one embodiment, modified kraft fiber is capable of absorbingodorants, such as nitrogen containing odorants, for example ammonia.

As used herein, the term “odorant” is understood to mean a chemicalmaterial that has a smell or odor, or that is capable of interactingwith olfactory receptors, or to mean an organism, such as a bacteria,that is capable of generating compounds that generate a smell or odor,for example a bacteria that produces urea.

In some embodiments, modified kraft fiber reduces atmospheric ammoniaconcentration more than a standard bleached kraft fiber reducesatmospheric ammonia. For example, modified kraft fiber may reduceatmospheric ammonia by absorbing at least part of an ammonia sampleapplied to modified kraft fiber, or by inhibiting bacterial ammoniaproduction. In at least one embodiment, modified kraft fiber absorbsammonia and inhibits bacterial ammonia production.

In some embodiments, modified kraft fiber reduces at least about 40%more atmospheric ammonia than standard kraft fibers, for example atleast about 50% more, or about 60% more, or about 70% more, or about 75%more, or about 80% more, or about 90% more ammonia than standard kraftfiber.

In some embodiments, modified kraft fiber of the disclosure, afterapplication of 0.12 g of a 50% solution of ammonium hydroxide to aboutnine grams of modified cellulose and a 45 minute incubation time,reduces atmospheric ammonia concentration in a volume of 1.6 L to lessthan 150 ppm, for example, less than about 125 ppm, for example lessthan bout 100 ppm, for example, less than about 75 ppm, for example,less than about 50 ppm.

In some embodiments, modified kraft fiber absorbs from about 5 to about10 ppm ammonia per gram of fiber. For instance, the modified cellulosemay absorb from about 6 to about 10 ppm, or from about 7 to about 10ppm, or from about 8 to about 10 ppm ammonia per gram of fibers.

In some embodiments, modified kraft fiber has both improved odor controlproperties and improved brightness compared to standard kraft fiber. Inat least one embodiment, modified cellulose fiber has a brightnessranging from about 85 to about 92 and is capable of reducing odor. Forexample, the modified cellulose may have a brightness ranging from about85 to about 92, and absorbs from about 5 to about 10 ppm ammonia forevery gram of fiber.

In some embodiments, modified cellulose fiber has an MEM ElutionCytotoxicity Test, ISO 10993-5, of less than 2 on a zero to four scale.For example the cytotoxicity may be less than about 1.5 or less thanabout 1.

It is known that oxidized cellulose, in particular cellulose comprisingaldehyde and/or carboxylic acid groups, exhibits anti-viral and/orantimicrobial activity. See, e.g., Song et al., Novel antiviral activityof dialdehyde starch, Electronic J. Biotech., Vol. 12, No. 2, 2009; U.S.Pat. No. 7,019,191 to Looney et al. For instance, aldehyde groups indialdehyde starch are known to provide antiviral activity, and oxidizedcellulose and oxidized regenerated cellulose, for instance containingcarboxylic acid groups, have frequently been used in wound careapplications in part because of their bactericidal and hemostaticproperties. Accordingly, in some embodiments, the cellulose fibers ofthe disclosure may exhibit antiviral and/or antimicrobial activity. Inat least one embodiment, modified cellulose fiber exhibits antibacterialactivity. In some embodiments, modified cellulose fiber exhibitsantiviral activity.

In some embodiments, modified kraft fiber of the disclosure has alevel-off DP of less than 200, such as less than about 100, or less thanabout 80, or less than about 75, or less than about 50 or less than orequal to about 48. Level-off DP can be measured by methods known in theart, for example by methods disclosed in Battista, et al., Level-OffDegree of Polymerization, Division of Cellulose Chemistry, Symposium onDegradation of Cellulose and Cellulose Derivatives, 127^(th) Meeting,ACS, Cincinnati, Ohio, March-April 1955.

In some embodiments modified kraft fiber has a kappa number of less thanabout 2. For example, modified kraft fiber may have a kappa number lessthan about 1.9. In some embodiments modified kraft fiber has a kappanumber ranging from about 0.1 to about 1, such as from about 0.1 toabout 0.9, such as from about 0.1 to about 0.8, for example from about0.1 to about 0.7, for instance from about 0.1 to about 0.6, such as fromabout 0.1 to about 0.5, or from about 0.2 to about 0.5.

In some embodiments, modified kraft fiber is kraft fiber bleached in amulti-stage process, wherein an oxidation step is followed by at leastone bleaching step. In such embodiments, the modified fiber after the atleast one bleaching step has a “k number”, as measured according toTAPPI UM 251, ranging from about 0.2 to about 1.2. For example, the knumber may range from about 0.4 to about 1.2, or from about 0.6 to about1.2, or from about 0.8 to about 1.2, or from about 1.0 to about 1.2.

In some embodiments, the modified cellulose fiber has a copper numbergreater than about 2. In some embodiments, the copper number is greaterthan 2.0. In some embodiments, the copper number is greater than about2.5. For example, the copper number may be greater than about 3. In someembodiments, the copper number ranges from about 2.5 to about 5.5, suchas from about 3 to about 5.5, for instance from about 3 to about 5.2.

In at least one embodiment, the hemicellulose content of the modifiedkraft fiber is substantially the same as standard unbleached kraftfiber. For example, the hemicellulose content for a softwood kraft fibermay range from about 16% to about 18%. For instance, the hemicellulosecontent of a hardwood kraft fiber may range from about 18% to about 25%.

III. Further Processing Acid/Alkaline Hydrolysis

In some embodiments, modified kraft fiber of the disclosure is suitablefor production of cellulose derivatives, for example for production oflower viscosity cellulose ethers, cellulose esters, and microcrystallinecellulose. In some embodiments, modified kraft fiber of the disclosureis hydrolyzed modified kraft fiber. As used herein “hydrolyzed modifiedkraft fiber,” “hydrolyzed kraft fiber” and the like are understood tomean fiber that has been hydrolyzed with any acid or alkaline treatmentknow to depolymerized the cellulose chain. In some embodiments, thekraft fiber according to the disclosure is further treated to reduce itsviscosity and/or degree of polymerization. For example, the kraft fiberaccording to the disclosure may be treated with an acid or a base.

In some embodiments, the disclosure provides a method of treating kraftfiber, comprising bleaching kraft fiber according to the disclosure, andthen hydrolyzing the bleached kraft fiber. Hydrolysis can be by anymethod known to those of ordinary skill in the art. In some embodiments,the bleached kraft fiber is hydrolyzed with at least one acid. In someembodiments, the bleached kraft fiber is hydrolyzed with an acid chosenfrom sulfuric acid, mineral acids, and hydrochloric acid.

The disclosure also provides a method for producing cellulose ethers. Insome embodiments, the method for producing cellulose ethers comprisesbleaching kraft fiber in accordance with the disclosure, treating thebleached kraft fiber with at least one alkali agent, such as sodiumhydroxide and reacting the fibers with at least one etherying agent.

The disclosure also provides methods for producing cellulose esters. Insome embodiments, the method for producing cellulose esters comprisesbleaching kraft fiber in accordance with the disclosure, treating thebleached kraft fiber with a catalyst, such as sulfuric acid, thentreating the fiber with at least one acetic anhydride or acetic acid. Inan alternative embodiment, the method for producing cellulose acetatescomprises bleaching kraft fiber in accordance with the disclosure,hydrolyzing the bleached kraft fiber with sulfuric acid, and treatingthe hydrolyzed kraft fiber with at least one acetic anhydride or aceticacid.

The disclosure also provides methods for producing microcrystallinecellulose. In some embodiments, the method for producingmicrocrystalline cellulose comprises providing bleached kraft fiberaccording to the disclosure, hydrolyzing the bleached kraft fiber withat least one acid until the desired DP is reached or under conditions toarrive at the level-off DP. In a further embodiment, the hydrolyzedbleached kraft fiber is mechanically treated, for example by grinding,milling, or shearing. Methods for mechanically treating hydrolyzed kraftfibers in microcrystalline cellulose production are known to persons ofskill in the art, and may provide desired particle sizes. Otherparameters and conditions for producing microcrystalline cellulose areknown, and are described for example in U.S. Pat. Nos. 2,978,446 and5,346,589.

In some embodiments, modified kraft fiber according to the disclosure isfurther treated with an alkaline agent or caustic agent to reduce itsviscosity and/or degree of polymerization. Alkaline treatment, a pHabove about 9, causes dialdehydes to react and undergo a beta-hydroxyelimination. This further modified fiber that has been treated with analkaline agent, may also be useful in the production of tissue, toweland also other absorbent products and in cellulose derivativeapplications. In more conventional papermaking, strength agents areoften added to the fiber slurry to modify the physical properties of theend products. This alkaline modified fiber may be used to replace someor all of the strength adjusting agent used in the production of tissueand towel.

As described above, there are three types of fiber products that can beprepared by the processes described herein. The first type is fiber thathas been treated by catalytic oxidation, which fiber is almostindistinguishable from its conventional counterpart (at least as far asphysical and papermaking properties are concerned), yet it hasfunctionality associated with it that gives it one or more of its odorcontrol properties, compressibility, low and ultra low DP, and/or theability to convert “in-situ” into a low DP/low viscosity fiber undereither alkaline or acid hydrolysis conditions, such as the conditions ofcellulose derivative production, e.g., ether or acetate production. Thephysical characteristics and papermaking properties of this type offiber make it appropriate for use in typical papermaking and absorbentproduct applications. The increased functionality, e.g., aldehydic andcarboxylic, and the properties associated with that functionality, onthe other hand, make this fiber more desirable and more versatile thanstandard kraft fiber.

The second type of fiber is fiber that has been subjected to catalyticoxidation and then has been treated with an alkaline or caustic agent.The alkaline agent causes the fiber to break down at the sites ofcarbonyl functionality that were added through the oxidation process.This fiber has different physical and papermaking properties than thefiber only subjected to oxidation, but may exhibit the same or similarDP levels since the test used to measure viscosity and thereby DPsubjects the fiber to a caustic agent. It would be evident to theskilled artisan that different alkaline agents and levels may providedifferent DP levels.

The third type of fiber is fiber that has been subjected to catalyticoxidation and then been treated in an acid hydrolysis step. The acidhydrolysis results in a breakdown of the fiber, possibly to levelsconsistent with its level-off DP.

IV. Products Made from Kraft Fibers

The present disclosure provides products made from the modified kraftfiber described herein. In some embodiments, the products are thosetypically made from standard kraft fiber. In other embodiments, theproducts are those typically made from cotton linter or sulfite pulp.More specifically, modified fiber of the present invention can be used,without further modification, in the production of absorbent productsand as a starting material in the preparation of chemical derivatives,such as ethers and esters. Heretofore, fiber has not been availablewhich has been useful to replace both high alpha content cellulose, suchas cotton and sulfite pulp, as well as traditional kraft fiber.

Phrases such as “which can be substituted for cotton linter (or sulfitepulp) . . . ” and “interchangeable with cotton linter (or sulfite pulp). . . ” and “which can be used in place of cotton linter (or sulfitepulp) . . . ” and the like mean only that the fiber has propertiessuitable for use in the end application normally made using cottonlinter (or sulfite pulp). The phrase is not intended to mean that thefiber necessarily has all the same characteristics as cotton linter (orsulfite pulp).

In some embodiments, the products are absorbent products, including, butnot limited to, medical devices, including wound care (e.g. bandage),baby diapers nursing pads, adult incontinence products, feminine hygieneproducts, including, for example, sanitary napkins and tampons, air-laidnon-woven products, air-laid composites, “table-top” wipers, napkin,tissue, towel and the like. Absorbent products according to the presentdisclosure may be disposable. In those embodiments, modified fiberaccording to the invention can be used as a whole or partial substitutefor the bleached hardwood or softwood fiber that is typically used inthe production of these products.

In some embodiments, modified cellulose fiber is in the form of fluffpulp and has one or more properties that make the modified cellulosefiber more effective than conventional fluff pulps in absorbentproducts. More specifically, modified fiber of the present invention mayhave improved compressibility and improved odor control, both of whichmake it desirable as a substitute for currently available fluff pulpfiber. Because of the improved compressibility of the fiber of thepresent disclosure, it is useful in embodiments which seek to producethinner, more compact absorbent structures. One skilled in the art, uponunderstanding the compressible nature of the fiber of the presentdisclosure, could readily envision absorbent products in which thisfiber could be used. By way of example, in some embodiments, thedisclosure provides an ultrathin hygiene product comprising the modifiedkraft fibers of the disclosure. Ultra-thin fluff cores are typicallyused in, for example, feminine hygiene products or baby diapers. Otherproducts which could be produced with the fiber of the presentdisclosure could be anything requiring an absorbent core or a compressedabsorbent layer. When compressed, fiber of the present inventionexhibits no or no substantial loss of absorbency, but shows animprovement in flexibility.

Modified fiber of the present invention may, without furthermodification, also be used in the production of absorbent productsincluding, but not limited to, tissue, towel, napkin and other paperproducts which are formed on a traditional papermaking machine.Traditional papermaking processes involve the preparation of an aqueousfiber slurry which is typically deposited on a forming wire where thewater is thereafter removed. The increased functionality of the modifiedcellulose fibers of the present disclosure may provide improved productcharacteristics in products including these modified fibers. For thereasons discussed above, the modified fiber of the present invention maycause the products made therewith to exhibit improvements in strength,likely associated with the increased functionality of the fibers. Themodified fiber of the invention may also result in products havingimproved softness.

In some embodiments, the modified fiber of the present disclosure,without further modification, can be used in the manufacture ofcellulose ethers (for example carboxymethylcellulose) and esters as asubstitute for fiber with very high DP from about 2950 to about 3980(i.e., fiber having a viscosity, as measured by 0.5% Capillary CED,ranging from about 30 mPa·s to about 60 mPa·s) and a very highpercentage of cellulose (for example 95% or greater) such as thosederived from cotton linters and from bleached softwood fibers producedby the acid sulfite pulping process. The modified fiber of the presentinvention which has not been subjected to acid hydrolysis will generallyreceive such an acid hydrolysis treatment in the production process forcreating cellulose ethers or esters.

As described, the second and third types of fiber are produced throughprocesses that derivatize or hydrolyze the fiber. These fibers can alsobe useful in the production of absorbent articles, absorbent paperproducts and cellulose derivatives including ethers and esters.

V. Acid/Alkaline Hydrolyzed Products

In some embodiments, this disclosure provides a modified kraft fiberthat can be used as a substitute for cotton linter or sulfite pulp. Insome embodiments, this disclosure provides a modified kraft fiber thatcan be used as a substitute for cotton linter or sulfite pulp, forexample in the manufacture of cellulose ethers, cellulose acetates andmicrocrystalline cellulose.

Without being bound by theory, it is believed that the increase inaldehyde content relative to conventional kraft pulp provides additionalactive sites for etherification to end-products such ascarboxymethylcellulose, methylcellulose, hydroxypropylcellulose, and thelike, enabling production of a fiber that can be used for bothpapermaking and cellulose derivatives.

In some embodiments, the modified kraft fiber has chemical propertiesthat make it suitable for the manufacture of cellulose ethers. Thus, thedisclosure provides a cellulose ether derived from a modified kraftfiber as described. In some embodiments, the cellulose ether is chosenfrom ethylcellulose, methylcellulose, hydroxypropyl cellulose,carboxymethyl cellulose, hydroxypropyl methylcellulose, and hydroxyethylmethyl cellulose. It is believed that the cellulose ethers of thedisclosure may be used in any application where cellulose ethers aretraditionally used. For example, and not by way of limitation, thecellulose ethers of the disclosure may be used in coatings, inks,binders, controlled release drug tablets, and films.

In some embodiments, the modified kraft fiber has chemical propertiesthat make it suitable for the manufacture of cellulose esters. Thus, thedisclosure provides a cellulose ester, such as a cellulose acetate,derived from modified kraft fibers of the disclosure. In someembodiments, the disclosure provides a product comprising a celluloseacetate derived from the modified kraft fiber of the disclosure. Forexample, and not by way of limitation, the cellulose esters of thedisclosure may be used in, home furnishings, cigarettes, inks, absorbentproducts, medical devices, and plastics including, for example, LCD andplasma screens and windshields.

In some embodiments, the modified kraft fiber has chemical propertiesthat make it suitable for the manufacture of microcrystalline cellulose.Microcrystalline cellulose production requires relatively clean, highlypurified starting cellulosic material. As such, traditionally, expensivesulfite pulps have been predominantly used for its production. Thepresent disclosure provides microcrystalline cellulose derived frommodified kraft fiber of the disclosure. Thus, the disclosure provides acost-effective cellulose source for microcrystalline celluloseproduction. In some embodiments, the microcrystalline cellulose isderived from modified kraft fiber having a DP which is less than about100, for example, less than about 75 or less than about 50. In someembodiments, the microcrystalline cellulose is derived from modifiedkraft fiber having an R10 value ranging from about 65% to about 85%, forinstance from about 70% to about 85%, or from about 75% to about 85% andan R18 value ranging from about 75% to about 90%, for instance fromabout 80% to about 90%, for example from about 80% to about 87%.

The modified cellulose of the disclosure may be used in any applicationthat microcrystalline cellulose has traditionally been used. Forexample, and not by way of limitation, the modified cellulose of thedisclosure may be used in pharmaceutical or nutraceutical applications,food applications, cosmetic applications, paper applications, or as astructural composite. For instance, the modified cellulose of thedisclosure may be a binder, diluent, disintegrant, lubricant, tablettingaid, stabilizer, texturizing agent, fat replacer, bulking agent,anticaking agent, foaming agent, emulsifier, thickener, separatingagent, gelling agent, carrier material, opacifier, or viscositymodifier. In some embodiments, the microcrystalline cellulose is acolloid

VI. Products Comprising Acid Hydrolyzed Products

In some embodiments, the disclosure provides a pharmaceutical productcomprising a microcrystalline cellulose that has been produced from amodified kraft fiber of the disclosure that has been hydrolyzed. Thepharmaceutical product may be any pharmaceutical product in whichmicrocrystalline cellulose has traditionally been used. For example, andnot by way of limitation, the pharmaceutical product may be chosen fromtablets and capsules. For instance, the microcrystalline cellulose ofthe present disclosure may be a diluent, a disintegrant, a binder, acompression aid, coating and/or a lubricant. In other embodiments, thedisclosure provides a pharmaceutical product comprising at least onemodified derivatized kraft fiber of the disclosure, such as a hydrolyzedmodified kraft fiber.

In some embodiments, the disclosure provides a food product comprising ableached kraft fiber of the disclosure that has been hydrolyzed. In someembodiments, the disclosure provides a food product comprising at leastone product derived from bleached kraft fiber of the disclosure. Infurther embodiments, the disclosure provides a food product comprisingmicrocrystalline cellulose derived from kraft fibers of the disclosure.In some embodiments, the food product comprises colloidalmicrocrystalline cellulose derived from kraft fibers of the disclosure.The food product may be any food product in which microcrystallinecellulose has traditionally been used. Exemplary food categories inwhich microcrystalline cellulose may be used are well known to those ofordinary skill in the art, and can be found, for example, in the CodexAlimentarius, for instance at Table 3. For instance, microcrystallinecellulose derived from chemically modified kraft fibers of thedisclosure may be an anticaking agent, bulking agent, emulsifier,foaming agent, stabilizer, thickener, gelling agent, and/or suspensionagent.

Other products comprising cellulose derivatives and microcrystallinecellulose derived from chemically modified kraft fibers according to thedisclosure may also be envisaged by persons of ordinary skill in theart. Such products may be found, for example, in cosmetic and industrialapplications.

As used herein, “about” is meant to account for variations due toexperimental error. All measurements are understood to be modified bythe word “about”, whether or not “about” is explicitly recited, unlessspecifically stated otherwise. Thus, for example, the statement “a fiberhaving a length of 2 mm” is understood to mean “a fiber having a lengthof about 2 mm.”

The details of one or more non-limiting embodiments of the invention areset forth in the examples below. Other embodiments of the inventionshould be apparent to those of ordinary skill in the art afterconsideration of the present disclosure.

EXAMPLES A. Test Protocols

-   -   1. Caustic solubility (R10, S10, R18, S18) is measured according        to TAPPI T235-cm00.    -   2. Carboxyl content is measured according to TAPPI T237-cm98.    -   3. Aldehyde content is measured according to Econotech Services        LTD, proprietary procedure ESM 055B.    -   4. Copper Number is measured according to TAPPI T430-cm99.    -   5. Carbonyl content is calculated from Copper Number according        to the formula: carbonyl=(Cu. No.−0.07)/0.6, from        Biomacromolecules 2002, 3, 969-975.    -   6. 0.5% Capillary CED Viscosity is measured according to TAPPI        T230-om99.    -   7. Intrinsic Viscosity is measured according to ASTM D1795        (2007).    -   8. DP is calculated from 0.5% Capillary CED Viscosity according        to the formula: DPw=−449.6+598.4 ln(0.5% Capillary CED)+118.02        ln² (0.5% Capillary CED), from the 1994 Cellucon Conference        published in The Chemistry and Processing Of Wood And Plant        Fibrous Materials, p. 155, woodhead Publishing Ltd, Abington        Hall, Abington, Cambridge CBI 6AH, England, J. F. Kennedy, et        al. editors.    -   9. Carbohydrates are measured according to TAPPI T249-cm00 with        analysis by Dionex ion chromatography.    -   10. Cellulose content is calculated from carbohydrate        composition according to the formula:        Cellulose=Glucan−(Mannan/3), from TAPPI Journal 65(12):78-80        1982.    -   11. Hemicellulose content is calculated from the sum of sugars        minus the cellulose content.    -   12. Fiber length and coarseness is determined on a Fiber Quality        Analyzer™ from OPTEST, Hawkesbury, Ontario, according to the        manufacturer's standard procedures.    -   13. Wet Zero Span Tensile is determined according to TAPPI        T273-pm99.    -   14. Freeness is determined according to TAPPI T227-om99.    -   15. Water Retention Value is determined according to TAPPI UM        256.    -   16. DCM (dichloromethane) extractives are determined according        to TAPPI T204-cm97.    -   17. Iron content is determined by acid digestion and analysis by        ICP.    -   18. Ash content is determined according to TAPPI T211-om02.    -   19. Peroxide residual is determined according to Interox        procedure.    -   20. Brightness is determined according to TAPPI T525-om02.    -   21. Porosity is determined according to TAPPI 460-om02.    -   22. Burst factor is determined according to TAPPI T403-om02.    -   23. Tear factor is determined according to TAPPI T414-om98.    -   24. Breaking length and stretch are determined according to        TAPPI T494-om01.    -   25. Opacity is determined according to TAPPI T425-om01.    -   26. Frazier porosity is determined on a Frazier Low Air        Permeability Instrument from Frazier Instruments, Hagerstown,        Md., according to the manufacturer's procedures.    -   27. Fiber Length and shape factor are determined on an L&W Fiber        Tester from Lorentzen & Wettre, Kista, Sweden, according to the        manufacturer's standard procedures.    -   28. Dirt and shives are determined according to TAPPI T213-om01

B. Exemplary Method for Making Modified Cellulose Fiber

A semi-bleached or mostly bleached kraft pulp may be treated with anacid, iron and hydrogen peroxide for the purposes of reducing thefiber's viscosity or DP. The fiber may be adjusted to a pH of from about2 to about 5 (if not already in this range) with sulfuric, hydrochloric,acetic acid, or filtrate from the washer of an acidic bleach stage, suchas a chlorine dioxide stage. Iron may be added in the form of Fe⁺², forexample iron may be added as ferrous sulfate heptahydrate (FeSO₄.7H₂O).The ferrous sulfate may be dissolved in water at a concentration rangingfrom about 0.1 to about 48.5 g/L. The ferrous sulfate solution may beadded at an application rate ranging from about 25 to about 200 ppm asFe⁺² based on the dry weight of pulp. The ferrous sulfate solution maythen be mixed thoroughly with the pH-adjusted pulp at a consistency offrom about 1% to about 15% measured as dry pulp content of the total wetpulp mass. Hydrogen peroxide (H₂O₂) may then be added as a solution witha concentration of from about 1% to about 50% by weight of H₂O₂ inwater, at an amount of from about 0.1% to about 3% based on the dryweight of the pulp. The pulp at a pH of from about 2 to about 5 mixedwith the ferrous sulfate and peroxide may be allowed to react for a timeranging from about 40 to about 80 minutes at a temperature of from about60 to about 80 degrees C. The degree of viscosity (or DP) reduction isdependent on the amount of peroxide consumed in the reaction, which is afunction of the concentration and amount of peroxide and iron appliedand the retention time and temperature.

The treatment may be accomplished in a typical five-stage bleach plantwith the standard sequence of D₀ E1 D1 E2 D2. With that scheme, noadditional tanks, pumps, mixers, towers, or washers are required. Thefourth or E2 stage may be preferably used for the treatment. The fiberon the D1 stage washer may be adjusted to a pH of from about 2 to about5, as needed by addition of acid or of filtrate from the D2 stage. Aferrous sulfate solution may be added to the pulp either (1) by sprayingit on the D1 stage washer mat through the existing shower headers or anew header, (2) added through a spray mechanism at the repulper, or (3)added through an addition point before a mixer or pump for the fourthstage. The peroxide as a solution may be added following the ferroussulfate at an addition point in a mixer or pump before the fourth stagetower. Steam may also be added as needed before the tower in a steammixer. The pulp may then be reacted in the tower for an appropriateretention time. The chemically modified pulp may then be washed on thefourth stage washer in a normal fashion. Additional bleaching may beoptionally accomplished following the treatment by the fifth or D2 stageoperated in a normal fashion.

Example 1 Methods of Preparing Fibers of the Disclosure

A. Mill Method A

Southern pine cellulose was digested and oxygen delignified in aconventional two-stage oxygen delignification step to a kappa number offrom about 9 to about 10. The delignified pulp was bleached in afive-stage bleach plant, with a sequence of D₀(EO)D1E2D2. Before thefourth or E2 stage, the pH of the pulp was adjusted to a range of fromabout 2 to about 5 with filtrate from a D stage of the sequence. Afterthe pH was adjusted, 0.2% hydrogen peroxide based on the dry weight ofthe pulp and 25 ppm Fe⁺² in the form of FeSO₄.7H₂O based on the dryweight of the pulp were added to the kraft fibers in the E2 stage towerand reacted for about 90 minutes at a temperature of from about 78 toabout 82 degrees C. The reacted fibers were then washed on the fourthstage washer, and then bleached with chlorine dioxide in the fifth (D2)stage.

B. Mill Method B

Fibers were prepared as described in Mill Method A, except that the pulpwas treated with 0.6% peroxide and 75 ppm Fe⁺².

C. Mill Method C

Fibers were prepared as described in Mill Method A, except that the pulpwas treated with 1.4% peroxide and 100 ppm Fe⁺².

Properties of Exemplary Fibers

Samples of fibers prepared according to Mill Methods A (sample 2), B(sample 3), and C (sample 4) were collected following the five-stagebleaching sequence described above. Several properties of these samplesalong with a standard fluff grade fiber (GP Leaf River Cellulose, NewAugusta, Miss.; Sample 1), and a commercially available sample (PEACH™,sold by Weyerhaeuser Co.; Sample 5), were measured according to theprotocols described above. The results of these measurements arereported in Table 1 below.

TABLE 1 Sample 1 GP Leaf River Sample 2 Sample 3 Sample 4 Sample 5Cellulose, fluff Mill Mill Mill Weyerhaeuser Fiber Measurement gradefiber Method A Method B Method C Co. PEACH R10 % 86.8 85.2 82.4 72.578.4 S10 % 13.2 14.8 17.6 27.5 21.6 R18 % 87.0 87.2 85.4 78.7 84.4 S18 %13.0 12.8 14.6 21.3 15.6 ΔR 0.2 2.0 3.0 6.2 6.0 Carboxyl meq/100 g 3.133.53 3.70 3.94 3.74 Aldehydes meq/100 g 0.97 1.24 2.15 4.21 0.87 CopperNo. 0.51 1.2 1.3 4.25 1.9 Calculated Carbonyl mmole/100 g 0.73 1.88 2.056.97 3.05 Calculated 0.75 1.52 0.95 1.66 3.5 carbonyl/Aldehyde ratio0.5% Capillary CED mPa · s 15.0 8.9 6.5 3.50 4.16 Viscosity IntrinsicViscosity [η] 

/g 7.14 5.44 4.33 2.49 3.00 Calculated DP DP_(w) 2036 1423 1084 485 643Glucan % 83.0 85.9 84.6 85.4 82 Xylan % 9.0 8.8 9.4 8.2 8.4 Galactan %0.2 0.2 0.2 0.2 0.2 Mannan % 5.9 5.4 5.3 5.5 6.2 Arabinan % 0.4 0.3 0.30.4 0.3 Calculated Cellulose % 81.0 84.1 82.8 83.6 79.9 Calculated %17.5 16.5 17.0 16.1 17.2 Hemicelllulose Lwl Fiber Length mm 2.34 2.572.53 2.30 2.19 Lww Fiber Length mm 3.39 3.34 3.34 3.01 Coarseness 0.2220.234 0.19 0.254 Wet Zero Span km 9.38 6.83 5.01 2.3 Breaking Length DCMextractives 0.006 0.006 Iron ppm 5.5 4.4 WRV 0.98 0.99 0.85 Brightness %ISO 89.6 89.0 88.2 88.5 88.5

As reported in Table 1, iron content of the control fiber, Sample 1, wasnot measured. However, the iron content of four mill-made pulp samplestreated under the same conditions as those reported for Sample 1 weretaken. The iron content of those samples averaged 2.6 ppm. Accordingly,for Sample 1, one would expect the iron content to be on the order ofabout 2.5 ppm.

As can be seen from Table 1, modified fiber according to the presentinvention is unexpectedly different from both the control fiber, Sample1, and an alternative commercially available oxidized fiber, Sample 5,in the total carbonyl content as well as the carboxyl content andaldehyde content. To the extent there is a difference between the totalcarbonyl groups and aldehyde groups, additional carbonyl functionalitymay be in the form of other ketones. The data shows that we achieverelatively high levels of aldehydes while retaining carboxylic acidgroups and while retaining a near unity ratio of aldehydes to totalcarbonyl groups (as seen in Table 1, about 1.0 (0.95) to 1.6). This ismore surprising in a fiber that exhibits high brightness and that isalso relatively strong and absorbent.

As can be seen in Table 1, the standard fluff grade fiber (Sample 1) hada carboxyl content of 3.13 meq/100 g, and an aldehyde content of 0.97meq/100 g. After a low-dose treatment with 0.2% H₂O₂ and 25 ppm Fe⁺²(Sample 2) or a higher-dose treatment with 0.6% H₂O₂ and 75 ppm Fe⁺²(Sample 3), or a higher-dose treatment with 1.4% H₂O₂ and 100 ppm Fe⁺²(Sample 4), the fiber length and calculated cellulose content wererelatively unchanged, and fiber strength as measured by the wet zerospan method was diminished somewhat, yet the carboxyl, carbonyl, andaldehyde contents were all elevated, indicating extensive oxidation ofthe cellulose.

In comparison, a commercially available sample of oxidized kraftsoftwood southern pine fiber manufactured by an alternative method(Sample 5), shows significant reduction in fiber length and about a 70percent loss in fiber strength as measured by the wet zero span methodas compared to the fluff grade fiber reported as Sample 1. The aldehydecontent of Sample 5 was virtually unchanged compared to the standardfluff grade fibers, while the inventive fibers prepared by mill methodsA-C (Samples 2-4) had highly elevated aldehyde levels representing fromabout 70 to about 100 percent of the total calculated carbonyl contentof the cellulose. In contrast, the PEACH® aldehyde level was less than30 percent of the total calculated carbonyl content of the cellulose.The ratio of total carbonyl to aldehyde would appear to be a goodindicator of a fiber that has the broad applicability of the modifiedfibers within the scope of this disclosure, particularly if the ratio isin the range of about 1 to about 2, as are Samples 2-4. Low viscosityfibers, such as Samples 3 and 4, and with carbonyl/aldehyde ratios ofabout 1.5 to less than 2.0, maintained fiber length, while those of thecomparative Sample 5 did not.

The freeness, density, and strength of the standard fiber describedabove (Sample 1) were compared with Sample 3 described above. Theresults of this analysis are depicted in Table 2.

TABLE 2 Pulp, Paper & Fiber Properties of Standard & Modified KraftFiber Wet Zero Span PFI Breaking Breaking refining Freeness DensityLength Length revs (CSF) g/cm³ km km Standard Leaf 0 737 0.538 2.16 9.38River Fluff 300 721 0.589 3.57 having 0.5% Capillary CED viscosity ofabout 15 mPa · s (Sample 1) Modified 0 742 0.544 2.19 6.83 cellulosefiber 300 702 0.595 3.75 as in (ULDP) having 0.5% Capillary CEDviscosity 6.5 mPa · s (Sample 3)

As can be seen in the above Table 2, the modified cellulose fibersaccording to this disclosure may have a freeness comparable to standardfluff fibers that have not undergone an oxidation treatment in thebleaching sequence.

Example 2

A sample of Southern pine pulp from the D1 stage of a OD(EOP)D(EP)Dbleach plant with a 0.5% Capillary CED viscosity of about 14.6 mPa·s wastreated at about 10% consistency with hydrogen peroxide applications offrom 0.25% to 1.5% and either 50 or 100 ppm of Fe⁺² added as FeSO₄.7H₂O.The Fe⁺² was added as a solution in water and mixed thoroughly with thepulp. The hydrogen peroxide as a 3% solution in water was then mixedwith the pulp. The mixed pulp was held in a water bath for 1 hour at 78°C. After the reaction time, the pulp was filtered and the filtratemeasured for pH and residual peroxide. The pulp was washed and the 0.5%Capillary CED viscosity determined according to TAPPI T230. The resultsare shown in Table 3.

TABLE 3 0.5% Cap- H₂O₂ H₂O₂ Fe⁺² illary CED added consumed ppm on pHViscosity % on pulp % on pulp pulp final mPa · s ΔViscosity DPw Control14.6 2003 0.25 0.25 100 4.8 8.6 6.0 1384 0.50 0.34 50 4.7 8.9 5.7 14230.50 0.50 100 4.8 6.8 7.8 1131 0.75 0.19 50 4.6 10.6 4.0 1621 0.75 0.75100 4.7 5.8 8.8 967 1.0 0.20 50 4.6 9.0 5.6 1435 1.0 0.40 100 4.7 7.86.8 1278 1.5 0.30 50 4.6 10.0 4.6 1554 1.5 0.40 100 4.6 7.5 7.1 1235

Example 3

A sample of D1 pulp from the bleach plant described in Example 2, with a0.5% Capillary CED viscosity of 15.8 mPa·s (DPw 2101) was treated with0.75% hydrogen peroxide applied and Fe⁺² was added from 50 to 200 ppm inthe same manner as Example 2, except the retention times were alsovaried from 45 to 80 minutes. The results are shown in Table 4.

TABLE 4 Treat- 0.5% Cap- ment H₂O₂ H₂O₂ Fe⁺² pH illary CED time addedconsumed ppm on fi- Viscosity ΔVis- DPw minutes % on pulp % on pulp pulpnal mPa · s cosity 2101 Control 15.8 1291 45 0.75 0.72 100 4.4 7.9 7.91035 60 0.75 0.75 200 4.1 6.2 9.6 1384 80 0.75 0.27 50 8.6 7.2 1018 800.75 0.75 100 4.6 6.1 9.7 2101

Example 4

A sample of D1 pulp from the bleach plant described in Example 2, with a0.5% Capillary CED viscosity of 14.8 mPa·s (DPw 2020) was treated with0.75% hydrogen peroxide and 150 ppm of Fe⁺² in the same manner asdescribed in Example 2, except that the treatment time was 80 minutes.The results are shown in Table 5.

TABLE 5 Treat- 0.5% Cap- ment H₂O₂ H₂O₂ Fe⁺² pH illary CED time addedconsumed ppm on fi- Viscosity ΔVis- minutes % on pulp % on pulp pulp nalmPa · s cosity DPw Control 14.8 2020 80 0.75 0.75 150 3.9 5.2 9.6 858

Example 5

A Southern pine pulp from the D1 stage of a OD₀(EO)D1(EP)D2 sequencewith a 0.5% Capillary CED viscosity of 15.6 mPa·s (DPw 2085) was treatedat 10% consistency with hydrogen peroxide applications of either 0.25%or 0.5% by weight on pulp and 25, 50, or 100 ppm of Fe⁺² added asFeSO₄.7H₂O. The Fe⁺² was added as a solution in water and mixedthoroughly with the pulp. The hydrogen peroxide was a 3% solution inwater that was then mixed with the pulp, and the mixed pulp was held ina water bath for 1 hour at 78° C. After the reaction time, the pulp wasfiltered and the filtrate measured for pH and residual peroxide. Thepulp was washed and the 0.5% Capillary CED viscosity determinedaccording to TAPPI T230. The results are shown in Table 6.

TABLE 6 0.5% Cap- H₂O₂ H₂O₂ Fe⁺² illary CED added consumed ppm on pHViscosity % on pulp % on pulp pulp final mPa · s ΔViscosity DPw Control15.6 2085 0.25 0.25 25 3.5 6.4 9.2 1068 0.50 0.50 50 2.9 4.5 11.1 7170.50 0.50 100 2.7 4.5 11.1 717

Example 6

Another sample of D1 pulp, with a 0.5% Capillary CED viscosity of 15.2mPa·s (DPw 2053) was treated with 0.10, 0.25, 0.50, or 0.65% hydrogenperoxide and 25, 50, or 75 ppm of Fe⁺² in the same manner as Example 5.The results are shown in Table 7.

TABLE 7 Treat- 0.5% Cap- ment H₂O₂ H₂O₂ Fe⁺² pH illary CED time addedconsumed ppm on fi- Viscosity ΔVis- minutes % on pulp % on pulp pulp nalmPa · s cosity DPw Control 15.2 2053 60 0.10 0.10 25 4.1 9.6 5.6 1508 600.25 0.19 25 4.0 7.9 7.3 1291 60 0.50 0.40 50 3.5 6.7 8.5 1116 80 0.650.65 75 3.3 4.4 10.8 696

Example 7

A Southern pine pulp was collected from the D1 stage of a OD(EO)D(EP)Dbleaching sequence, after the extent of delignification in the kraft andoxygen stages was increased to produce a pulp with a lower DPw or 0.5%Capillary CED viscosity. The starting 0.5% Capillary CED viscosity was12.7 mPa·s (DPw 1834). Either 0.50 or 1.0% hydrogen peroxide was addedwith 100 ppm of Fe⁺². Other treatment conditions were 10% consistency,78° C., and 1 hour treatment time. The results are shown in Table 8.

TABLE 8 0.5% Cap- H₂O₂ H₂O₂ Fe⁺² illary CED added consumed ppm on pHViscosity % on pulp % on pulp pulp final mPa · s ΔViscosity DPw Control12.7 1834 0.50 0.50 100 2.1 5.6 7.1 932 1.0  0.37 100 2.6 4.2 8.5 652

Example 8

A low viscosity sample of D1 pulp from the D1 stage of a OD(EO)D(EP)Dsequence, with a 0.5% Capillary CED viscosity of 11.5 mPa·s (DPw 1716),was treated with either 0.75 or 1.0% hydrogen peroxide and 75 or 150 ppmof Fe⁺² in a manner similar to Example 7, except the treatment time was80 minutes. The results are shown in Table 9.

TABLE 9 0.5% Cap- H₂O₂ H₂O₂ Fe⁺² illary CED added consumed ppm on pHViscosity % on pulp % on pulp pulp final mPa · s ΔViscosity DPw Control11.5 1716 0.75 0.75 75 3.2 3.6 7.9 511 0.75 0.75 150 3.0 3.8 7.7 560 1 175 2.6 3.4 8.1 459 1 1 150 2.6 3.4 8.1 459

Example 9

A Southern pine pulp was collected from the D1 stage of a OD(EO)D(EP)Dsequence. The starting 0.5% Capillary CED viscosity was 11.6 mPa·s (DPw1726). Either 1.0%, 1.5%, or 2% hydrogen peroxide was added with 75,150, or 200 ppm of Fe⁺². Other treatment conditions were 10%consistency, 78° C., and 1.5 hour treatment time. The results are shownin Table 10.

TABLE 10 0.5% Cap- H₂O₂ H₂O₂ Fe⁺² illary CED Carboxyl Aldehyde addedconsumed ppm on pH Viscosity meq/100 meq/100 Copper % on pulp % on pulppulp final mPa · s ΔViscosity DPw g g no. Control 11.6 1726 3.67 0.350.52 1.0 0.98 75 3.4 3.5 8.1 485 3.73 4.06 3.05 1.5 1.49 150 2.7 3.2 8.4406 3.78 5.06 2.57 2.0 2.0 200 2.9 3.0 8.6 350 3.67 5.23 2.06

Example 10

A Southern pine pulp was collected from the D1 stage of a OD(EO)D(EP)Dsequence. The starting 0.5% Capillary CED viscosity was 14.4 mPa·s (DPw1986). Either 1.0%, 1.5%, or 2% hydrogen peroxide was added with 75,150, or 200 ppm of Fe⁺². Other treatment conditions were 10%consistency, 78° C., and 1.5 hour reaction time. The results are shownin Table 11.

TABLE 11 0.5% Cap- H₂O₂ H₂O₂ Fe⁺² illary CED Carboxyl Aldehyde addedconsumed ppm on pH Viscosity meq/100 meq/100 Copper % on pulp % on pulppulp final mPa · s ΔViscosity DPw g g no. Control 14.4 1986 3.52 0.230.67 1.0 0.95 75 3.3 3.8 10.6 560 3.65 3.48 2.47 1.5 1.5 150 2.4 3.710.7 535 4.13 4.70 2.32 2.0 2.0 200 2.8 3.2 11.2 406 3.93 5.91 1.88

Example 11

A Southern pine pulp was collected from the D1 stage of a OD(EO)D(EP)Dsequence. The starting 0.5% Capillary CED viscosity was 15.3 mPa·s (DPw2061). Hydrogen peroxide was added at 3% on pulp with 200 ppm of Fe⁺².Other treatment conditions were 10% consistency, 80° C., and 1.5 hourreaction time. The results are shown in Table 12.

TABLE 12 0.5% Cap- H₂O₂ H₂O₂ Fe⁺² illary CED Carboxyl Aldehyde addedconsumed ppm on pH Viscosity meq/100 meq/100 Copper % on pulp % on pulppulp final mPa · s ΔViscosity DPw g g no. Control 15.3 2061 3.0 2.9 2002.8 2.94 12.4 333 4.66 6.74 5.14

The above Examples 2-11 show that a significant decrease in 0.5%Capillary CED viscosity and/or degree of polymerization can be achievedwith the acidic, catalyzed, peroxide treatment of the presentdisclosure. The final viscosity or DPw appears to be dependent on theamount of peroxide that is consumed by the reaction, as shown in FIG. 1,which reports the viscosity of pulp from two different mills(“Brunswick” and Leaf River (“LR”)) as a function of the percentperoxide consumed. The peroxide consumption is a function of the amountsand concentrations of peroxide and iron applied, the reaction time, andthe reaction temperature.

Example 12

A Southern pine pulp was collected from the D1 stage of a OD(EO)D(EP)Dsequence. The starting 0.5% Capillary CED viscosity was 14.8 mPa·s (DPw2020). Hydrogen peroxide was added at 1% on pulp with either 100, 150,or 200 pm of Cu⁺² added as CuSO₄.5H₂O. Other treatment conditions were10% consistency, 80° C., and 3.5 hours reaction time. The results areshown in Table 13.

TABLE 13 0.5% Cap- H₂O₂ H₂O₂ Cu⁺² illary CED Carboxyl Aldehyde addedconsumed ppm on pH Viscosity meq/100 meq/100 Copper % on pulp % on pulppulp final mPa · s ΔViscosity Dpw g g no. Control 14.8 2020 3.36 0.370.51 1.0 0.82 100 2.4 6.1 8.7 1018 1.0 0.94 150 2.3 5.9 8.9 984 1.0 0.94200 2.4 6.0 8.8 1001 3.37 2.71 1.8

The use of copper instead of iron resulted in a slower reaction and alower reduction in viscosity, but still a significant change inviscosity, carboxyl content, and aldehyde content over the control,untreated pulp.

Example 13

The E2 (EP) stage of an OD(EOP)D(EP)D sequence was altered to producethe ultra low degree of polymerization pulp. A solution of FeSO₄.7H₂Owas sprayed on the pulp at the washer repulper of the D1 stage at anapplication rate of 150 ppm as Fe⁺². No caustic (NaOH) was added to theE2 stage and the peroxide application was increased to 0.75%. Theretention time was approximately 1 hour and the temperature was 79° C.The pH was 2.9. The treated pulp was washed on a vacuum drum washer andsubsequently treated in the final D2 stage with 0.7% ClO₂ forapproximately 2 hours at 91° C. The 0.5% Capillary CED viscosity of thefinal bleached pulp was 6.5 mPa·s (DPw 1084) and the ISO brightness was87.

Example 14

The pulp produced in Example 13 was made into a pulp board on aFourdrinier type pulp dryer with standard dryer cans. Samples of acontrol pulp and the pulp of the present invention (ULDP) were collectedand analyzed for chemical composition and fiber properties. The resultsare shown in Table 14.

TABLE 14 Property Standard ULDP R10 % 85.2 81.5 S10 % 14.8 18.5 R18 %86.4 84.4 S18 % 13.6 15.6 ΔR 1.2 2.9 Carboxyl meq/100 g 4.06 4.27Aldehydes meq/100 g 0.43 1.34 Copper No. 0.32 1.57 Calculated Carbonylmmole/100 g 0.42 2.50 0.5% Capillary CED Viscosity mPa · s 14.2 7.3Intrinsic Viscosity dl/g 6.76 4.37 Calculated DP DP_(w) 1969 1206 Glucan% 83.6 83.6 Xylan % 9.2 9.0 Galactan % 0.2 0.2 Mannan % 6.3 6.4 Arabinan% 0.4 0.4 Calculated Cellulose % 81.5 81.5 Calculated Hemicelllulose %18.2 18.1 Lwl Fiber Length mm 2.51 2.53 Lww Fiber Length mm 3.28 3.26Coarseness mg/m 0.218 0.213 Wet Zero Span Tensile km 9.86 6.99 Freeness(CSF) mls 720 742 Water Retention Value g H₂O/g pulp 0.96 0.84 DCMextractives 0.008 0.007 Iron ppm 3.5 10.7 Ash % 0.20 0.22 Brightness %ISO 90.4 86.5

The treated pulp (ULDP) had a higher alkali solubility in 10% and 18%NaOH and a higher aldehyde and total carbonyl content. The ULDP wassignificantly lower in DP as measured by 0.5% Capillary CED viscosity.The decrease in fiber integrity was also determined by a reduction inwet zero span tensile strength. Despite the significant reduction inDPw, the fiber length and freeness were essentially unchanged. Therewere no deleterious effects on drainage or board making on the machine.

Example 15

The E2 (EP) stage of a OD(EO)D(EP)D sequence was altered to produce theultra low degree of polymerization pulp in a similar manner as Example13. In this example, the FeSO₄.7H₂O was added at 75 ppm as Fe⁺² and thehydrogen peroxide applied in the E2 stage was 0.6%. The pH of thetreatment stage was 3.0, the temperature was 82° C., and the retentiontime was approximately 80 minutes. The pulp was washed and then treatedin a D2 stage with 0.2% ClO₂ at 92° C. for approximately 150 minutes.The 0.5% Capillary CED viscosity of the fully bleached pulp was 5.5mPa·s (DPw 914) and the ISO brightness was 88.2.

Example 16

The pulp produced in Example 15 was made into a pulp board on aFourdrinier type pulp dryer with an airborne Flakt™ dryer section.Samples of a standard pulp and the pulp of the present invention (ULDP)were collected and analyzed for chemical composition and fiberproperties. The results are shown in Table 15.

TABLE 15 Property Standard ULDP R10 % 86.8 82.4 S10 % 13.2 17.6 R18 %87.0 85.4 S18 % 13.0 14.6 ΔR 0.2 3.0 Carboxyl meq/100 g 3.13 3.70Aldehydes meq/100 g 0.97 2.15 Copper No. 0.51 1.3 Calculated Carbonylmmole/100 g 0.73 2.05 0.5% Capillary CED mPa · s 15.0 6.5 ViscosityIntrinsic Viscosity dl/g 7.14 4.33 Calculated DP DP_(w) 2036 1084 Glucan% 83.0 84.6 Xylan % 9.0 9.4 Galactan % 0.2 0.2 Mannan % 5.9 5.3 Arabinan% 0.4 0.3 Calculated Cellulose % 81.0 82.8 Calculated Hemicelllulose %17.5 17.0 Lwl Fiber Length mm 2.55 2.53 Lww Fiber Length mm 3.29 3.34Coarseness mg/m 0.218 0.234 Wet Zero Span Tensile km 9.38 6.83 Freeness(CSF) mls 738 737 Iron ppm 1.6 4.4 Brightness % ISO 89.6 88.2

The treated pulp (ULDP) had a higher alkali solubility in 10% and 18%NaOH and a higher aldehyde and total carbonyl content. The ULDP wassignificantly lower in DP as measured by 0.5% Capillary CED viscosityand lower wet zero span breaking length. The brightness was still anacceptable value of 88.2. The treatment preserved the fiber length andfreeness and there were no operational issues forming and drying theboard.

Example 17

The E2 (EP) stage of a OD(EO)D(EP)D sequence was altered to produce alow degree of polymerization pulp in a similar manner as Example 13. Inthis case the FeSO₄.7H₂O was added at 25 ppm as Fe⁺² and the hydrogenperoxide applied in the E2 stage was 0.2%. The pH of the treatment stagewas 3.0, the temperature was 82° C. and the retention time wasapproximately 80 minutes. The pulp was washed then treated in a D2 stagewith 0.2% ClO₂ at 92° C. for approximately 150 minutes. The 0.5%Capillary CED viscosity of the fully bleached pulp was 8.9 mPa·s (DPw1423) and the ISO brightness was 89.

Example 18

The pulp produced in Example 15 was made into a pulp board on aFourdrinier type pulp dryer with an airborne Flakt™ dryer section.Samples of a standard pulp and the low degree of polymerization pulp ofthe present invention (LDP) were collected and analyzed for chemicalcomposition and fiber properties. The results are shown in Table 16.

TABLE 16 Property Standard LDP R10 % 86.8 85.2 S10 % 13.2 14.8 R18 %87.0 87.2 S18 % 13.0 12.8 ΔR 0.2 2.0 Carboxyl meq/100 g 3.13 3.53Aldehydes meq/100 g 0.97 1.24 Copper No. 0.51 1.2 Calculated Carbonylmmole/100 g 0.73 1.88 0.5% Capillary CED mPa · s 15.0 8.9 ViscosityIntrinsic Viscosity dl/g 7.14 5.44 Calculated DP DP_(w) 2036 1423 Glucan% 83.0 85.9 Xylan % 9.0 8.8 Galactan % 0.2 0.2 Mannan % 5.9 5.4 Arabinan% 0.4 0.3 Calculated Cellulose % 81.0 84.1 Calculated Hemicelllulose %17.5 16.5 Lwl Fiber Length mm 2.55 2.57 Lww Fiber Length mm 3.29 3.34Coarseness mg/m 0.218 0.222 Iron ppm 1.6 5.5 Brightness % ISO 89.6 89.0

The treated pulp (LDP) had a higher alkali solubility in 10% and 18%NaOH and a higher aldehyde and total carbonyl content. The LDP was lowerin DP as measured by 0.5% Capillary CED viscosity. There was a minimalloss in brightness. The treatment preserved the fiber length and therewere no operational issues forming and drying the board.

Example 19

The pulp boards described in Example 14 were fiberized and airformedinto 4″×7″ pads using a Kamas Laboratory Hammermill (Kamas Industries,Sweden). The airformed pads were then compressed at various gaugepressures using a laboratory press. After pressing, the pad caliper wasmeasured using an Emveco microgage caliper gage model 200-A with a footpressure of 0.089 psi. Pad density was calculated from the pad weightand caliper. The results are depicted in Table 17.

TABLE 17 Gauge Pressure 5 psi 10 psi 20 psi Caliper Pad Density CaliperPad Density Caliper Pad Density mm Wt g g/cc mm Wt g g/cc mm Wt g g/ccStandard 2.62 5.14 0.108 2.29 5.27 0.127 1.49 5.29 0.196 Kraft 2.81 5.140.101 2.26 5.19 0.127 1.42 5.23 0.203 Southern Pine Fiber Modified 2.515.16 0.114 2.13 5.33 0.138 1.23 5.39 0.242 Kraft 2.56 5.26 0.114 1.935.37 0.154 1.32 5.26 0.220 Southern Pine Fiber Percent 8.43 14.94 15.67Increase in Density

The data in Table 17 show that the modified fibers produced within thescope of this disclosure were more compressible, resulting in thinnerand higher density structures more suitable for today's disposableabsorbent product designs.

Without being bound by theory, it is believed that the oxidation of thecellulose disrupts the crystalline structure of the polymer, renderingit less stiff and more conformable. The fibers composed of the modifiedcellulose structure then become more compressible, allowing for theproduction of higher density absorbent structures.

Example 20

A Southern pine pulp was collected from the D1 stage of a OD(EO)D(EP)Dsequence. The starting 0.5% Capillary CED viscosity was 14.9 mPa·s (DPw2028). Either 1.0% or 2% hydrogen peroxide was added with 100 or 200 ppmof Fe⁺² respectively. Other treatment conditions were 10% consistency,80° C., and 1 hour retention time. These fluff pulps were then slurriedwith deionized water, wetlaid on a screen to form a fiber mat, dewateredvia roller press, and dried at 250° F. The dry sheets were defibratedand airformed into 4″×7″ airlaid pads weighing 8.5 grams (air dried)using a Kamas Laboratory Hammermill (Kamas Industries, Sweden). Asingle, complete coverage sheet of nonwoven coverstock was applied toone face of each pad and the samples were densified using a Carverhydraulic platen press applying a load of 145 psig.

These pads were placed in individual 1.6 L airtight plastic containershaving a removable lid fitted with a check valve and sampling port of ¼″ID Tygon® tubing. Before securing the lid of the container, an insult of60 grams deionized water and 0.12 gram 50% NH₄OH at room temperature waspoured into a centered 1″ ID vertical tube on a delivery device capableof applying a 0.1 psi load across the entirety of the sample. Upon fullabsorption of the insult, the delivery device was removed from thesample, the lid, with sealed sampling port, was fitted to the container,and a countdown timer started. At the conclusion of 45 minutes, aheadspace sample was taken from the sampling port with anammonia-selective short-term gas detection tube and ACCURO® bellowspump, both available from Draeger Safety Inc., Pittsburgh, Pa. The datain Table 18 show that the modified fibers produced within the scope ofthis disclosure were able to reduce the amount of ammonia gas in theheadspace, resulting in a structure that provides suppression of avolatile malodorous compound often cited as unpleasant in wettedincontinence products.

TABLE 18 0.5% CED Aldehyde Air Ammonia Insult-60 g H₂0/ ViscosityContent Laid Pad (ppm) 0.12 g 50% NH₄OH (mPa · s) meq/100 g Weight (g) @45 mins Standard Kraft 14.9 0.23 9.16 210 Southern Pine Fiber ModifiedKraft 4.7 3.26 9.11 133 Southern Pine Fiber- 1.0% H₂O₂/100 ppm FeModified Kraft 3.8 4.32 9.23 107 Southern Pine Fiber- 2.0% H₂O₂/200 ppmFe

Example 21

The E2 stage of a OD(EO)D(EP)D sequence of a commercial kraft pulpingfacility was altered to produce the low degree of polymerization pulp ina similar manner as Example 14. In this example, the FeSO₄.7H₂O wasadded at 100 ppm as Fe⁺² and the hydrogen peroxide applied in the E2stage was 1.4%. The pulp properties are shown in Table 19.

TABLE 19 Property ULDP R10 % 72.5 S10 % 27.5 R18 % 78.7 S18 % 21.3 ΔR6.2 Carboxyl meq/100 g 3.94 Aldehydes meq/100 g 4.21 Copper No. 4.25Calculated Carbonyl mmole/100 g 6.97 0.5% Capillary CED mPa · s 3.50Viscosity Intrinsic Viscosity dl/g 2.49 Calculated DP DP_(w) 485 LwlFiber Length mm 2.31 Coarseness mg/m 0.19 Brightness % ISO 88.5

The modified chemical cellulose produced was made into a pulp board on aFourdrinier type pulp dryer with an airborne Flakt™ dryer section.Samples of this product and control kraft pulp board were defibratedusing the Kamas laboratory hammermill. Optical analysis of fiberproperties were performed on both pre and post Kamas mill samples viaHiRes Fiber Quality Analyzer available from Optest Equipment, Inc.,Hawkesbury, ON, Canada, according to the manufacturer's protocols. Theresults are depicted in the table below.

TABLE 20 ULDP Control post- Property Control ULDP post-hammermillhammermill Kink index 1.79 2.29 1.51 2.32 Kink angle 59.15 79.56 48.5280.26 Kinks per mm 0.81 1.07 0.68 1.06 Curl Index 0.171 0.211 0.1490.225 (length weighted)

As can be seen in Table 20, the ULDP fibers prepared in accordance withthe disclosure have higher kink and curl than control fibers not treatedwith iron and peroxide.

The defibrated fibers above were airformed into 4″×7″ pads weighing 4.25grams (air-dried). Sodium polyacrylate superabsorbent (SAP) granulessourced from BASF were applied evenly between two 4.25 gram pads. A fullcoverage nonwoven coverstock was applied to the top face of thefiber/SAP matrix and the pad was densified by a load of 145 psig appliedvia Carver platen press.

Synthetic urine was prepared by dissolving 2% Urea, 0.9% SodiumChloride, and 0.24% nutrient broth (Criterion™ brand available throughHardy Diagnostics, Santa Maria, Calif.) in deionized water, and addingan aliquot of Proteus Vulgaris resulting in a starting bacterialconcentration of 1.4×10⁷ CFU/ml. The pad described above was then placedin a headspace chamber as described in Example 20 and insulted with 80ml of the synthetic urine solution. Immediately after insult, thechamber was sealed and placed in an environment with a temperature of30° C. Dräger sampling was performed in series at time intervals of fourhours and seven hours. The experiment was repeated three times, and theaverage results are reported in Table 21.

TABLE 21 % % SAP Ammonia reduction Ammonia % reduction add (ppm) @ over(ppm) @ over on 4 hrs control 7 hrs control Modified Kraft 23 2.5 29Southern Pine Fiber Control Kraft 23 21.5 88 175 83 Southern Pine FiberModified Kraft 16.5 6.5 123 Southern Pine Fiber Control Kraft 16.5 36.582 550 78 Southern Pine Fiber Modified Kraft 0 70 317 Southern PineFiber Control Kraft 0 197.5 65 575 45 Southern Pine Fiber

As can be seen from the data, atmospheric ammonia resulting frombacterial hydrolysis of urea is lower in composite structures (similarin construction to retail urinary incontinence products) incorporatingmodified cellulose fibers produced within the scope of this disclosureversus composite structures produced with standard kraft southern pinefibers. Thus, structures comprising modified cellulose fibers accordingto the disclosure had better odor control properties than standard kraftsouthern pine fibers.

Example 22 Comparison of 4th Stage to Post-Bleach Treatment

A Southern pine pulp was collected from the D1 stage of a OD(E0)D1(EP)D2sequence. The starting 0.5% Capillary CED viscosity was 14.1 mPa·s.Hydrogen peroxide was added as 1.5% based on the dry weight of the pulpwith 150 ppm of Fe⁺². As used herein, “P*” is used to indicate an ironand hydrogen peroxide treatment stage The treatment was conducted at 10%consistency at a temperature of 78° C. for 1 hour in the fourth stage ofthe sequence. This treated pulp was then washed and bleached in D2 stagewith 0.25% ClO₂ for 2 hours at 78° C. The results are shown in Table 22.

TABLE 22 0.5% Capillary Length weighted Chemical added pH CED ViscosityBrightness Fiber Length Stage % on pulp final mPa · s ΔViscosity DPw %ISO mm D1 14.1 1960 83.5 P* 1.5% H₂O₂ 150 ppm Fe⁺² 3.1 82.0 D2 0.25%ClO₂ 2.7 3.7 10.4 540 89.5 2.20

The D2 sample above was also tested for brightness reversion by placingit in an oven at 105° C. for 1 hour. The brightness as well as L*(whiteness), a* (red to green), and b* (blue to yellow) values weremeasured by a Hunterlab MiniScan, according to the manufacturer'sprotocols, before and after the reversion treatment. The results areshown in Table 23 below. More positive b values indicate a more yellowcolor. Thus, higher b values are undesirable in most paper and pulpapplications. Post color number, reported below, represents thedifference in the ratio k/s before and after aging, where k=absorptioncoefficient and s=scattering coefficient. i.e., post colorno.=100{(k/s)_(after aging)−(k/s)_(before aging)}. See, e.g., H. W.Giertz, Svensk Papperstid., 48(13), 317 (1945).

TABLE 23 Brightness Reversion Bright- ΔBright- Post Stage L* a* b* nessness Color No. D1 96.89 −0.28 5.13 85.8 DP*D initial 97.89 −0.47 2.9690.8 DP*D reverted 96.08 −0.55 8.01 80.4 10.4 1.92

A Southern pine pulp was collected from the D2 stage of the same bleachplant as above with the same starting Capillary CED viscosity and wastreated with hydrogen peroxide and Fe⁺² as described above. Hydrogenperoxide was added as 1.5% based on the dry weight of the pulp with 150ppm of Fe⁺². The properties of this treated pulp are depicted in Table24.

TABLE 24 0.5% Capillary Length weighted Chemical added pH CED ViscosityBrightness Fiber Length Stage % on pulp final mPa · s ΔViscosity DPw %ISO mm D2 14.1 1960 90.2 P* 1.5% H₂O₂ 150 ppm Fe⁺² 2.8 3.5 10.6 485 86.82.17

The P* pulp was tested for brightness reversion as described above. Theresults are depicted in Table 25 below.

TABLE 25 Brightness Reversion Bright- ΔBright- Post Stage L* a* b* nessness Color No. D2 Initial 98.34 −0.61 2.54 92.54 D2 Reverted 97.87 −0.573.67 89.92 2.62 0.26 D(EP)DP* 97.39 −0.47 4.49 87.68 initial D(EP)DP*95.25 −0.34 9.78 76.45 11.2 2.76 reverted

As can be seen from the above data, acidic catalyzed peroxide treatmentin the fourth stage of a five-stage bleach plant compared to treatmentfollowing the final stage of a five-stage bleach plant results inbeneficial brightness properties. In the fourth stage treatment, anybrightness loss from the treatment stage can be compensated for with thefinal D2 bleaching stage so that a high brightness pulp is stillobtained. In the case of post-bleach treatment, there is a significantbrightness loss of 3.4 points that cannot be compensated for. After anaccelerated brightness reversion treatment, the latter case still has asignificantly lower brightness.

Example 23 Strength Data

The strength of fluff pulp produced from modified cellulose with aviscosity of 5.1 mPa·s according to the disclosure was compared withconventional fluff pulp having a viscosity of 15.4 mPa·s. The resultsare depicted in Table 26 below.

TABLE 26 Control Modified Fluff Cellulose Basis Wt., gm/m² AD 65.1268.15 Basis Wt., gm/m² OD 60.56 63.38 Freeness CSF, mls 732 717 Caliper,in/1000 4.88 5.09 Bulk, cm³/gm 1.90 1.90 Apparent Density, gm/cm³ 0.530.53 Porosity, sec/100 mls air 0.59 0.67 Burst Factor, (gm/cm²)/(gm/m²)16.6 14.0 Tear Factor, gf * m²/gm 242 198 Breaking Length, km 2.52 2.49Stretch, % 2.76 2.48 Opacity, % 72.1 73.5 Dirt and Shives, mm²/m² 0.31.5 Viscosity, cP 15.4 5.1 ISO Brightness 88.9 88.9 Frazier Porosity,cfm 45.4 55.1 Fiber Length, mm 2.636 2.661 Shape Factor, % 85.8 85.8

Example 24 Derivatization of Modified Cellulose

A sample of ULDP from Example 21 was acid hydrolyzed with 0.05 M HCl at5% consistency for 3 hours at 122° C. The initial pulp from the D1stage, the ULDP, and the acid hydrolyzed ULDP were tested for averagemolecular weight or degree of polymerization by the method below.

Three pulp samples were grounded to pass a 20 mesh screen. Cellulosesamples (15 mg) were placed in separate test tubes equipped with microstir bars and dried overnight under vacuum at 40° C. The test tubes werethen capped with rubber septa. Anhydrous pyridine (4.00 mL) and phenylisocyanate (0.50 mL) were added sequentially via syringe. The test tubeswere placed in an oil bath at 70° C. and allowed to stir for 48 h.Methanol (1.00 mL) was added to quench any remaining phenyl isocyanate.The contents of each test tube were then added dropwise to a 7:3methanol/water mixture (100 mL) to promote precipitation of thederivatized cellulose. The solids were collected by filtration and thenwashed with methanol/water (1×50 mL) followed by water (2×50 mL). Thederivatized cellulose was then dried overnight under vacuum at 40° C.Prior to GPC analysis the derivatized cellulose was dissolved in THF (1mg/mL), filtered through a 0.45 μm filter, and placed in a 2 mLauto-sampler vial. The resulting DPw and DPn (number average degree ofpolymerization) are reported in Table 27 below.

TABLE 27 DPn and DPw test results Sample Mn (g/mol) Mw (g/mol) DPn DPwD1 1.4601e5 2.2702e6 281 4374 ULDP 4.0775e4 7.4566e5 78 1436 AcidHydrolyzed  2.52.5e4 1.8966e5 48 365 ULDP

As can be seen in the above table, modified cellulose after acidhydrolysis according to the disclosure can have a DPn of 48.

Example 25

Leaf River ULDP fibers and standard softwood fibers were made intohandsheets by slurrying the fiber, adjusting the pH to about 5.5, andthen adding, as a temporary wet strength agent, a glyoxylatedpolyacrylamide from Kemira Chemicals. The fibers were then formed,pressed into sheets and dried. The characteristics of the sheets weremeasured by known methods. The results are reported in Table 28 below.

TABLE 28 Handsheet properties LR SW (Control) ULDP TWS #T 0 10 20 40 010 20 40 Titratable mL/10 −0.166 +0.204 +0.389 +2.899 −0.143 −0.134+0.474 +1.919 Charge mL 10- 3N Basis #/R 15.11 16.19 15.59 14.64 15.7514.83 13.08 15.3 Weight g/m2 24.59 26.35 25.37 23.83 25.63 24.14 21.2924.9 Bulk 1-ply 3.68 3.78 3.80 4.04 3.80 3.72 4.12 4.08 Caliper, milsBulk, 3.80 3.64 3.80 4.31 3.77 3.91 4.92 4.16 cm3/g Dry Tensile, 7471335 1187 1118 716 825 866 864 Tensile g/1″ Breaking 1.196 1.995 1.8421.847 1.100 1.346 1.602 1.366 Length, km Stretch, % 2.6 3.2 2.9 3.0 2.22.7 3.3 2.9 T.E.A., 0.10 0.28 0.21 0.21 0.06 0.11 0.17 0.12 mm- gm/mm²Wet Tensile, 4 209 218 256 23 148 200 168 Tensile g/1″ Breaking 0.00640.3123 0.3383 0.423 0.0353 0.2414 0.3699 0.2656 Length, km SAT Capacity,205.9 194.7 187.0 190.9 185.0 173.0 182.0 202.0 g/m² Rate, 0.06 0.080.07 0.05 0.08 0.07 0.07 0.10 g/s^(0.5) Time, 89.6 59.1 59.2 83.8 55.550.0 57.7 49.9 s Wet/Dry 1% 16% 18% 23% 3% 18% 23% 19% ratio

As can be seen in the above Table 28, ULDP according to the disclosuremay be used in production of wet pressed paper. As is shown in FIG. 2,the wet/dry ratio of the handsheets formed from ULDP is higher than thewet/dry ratio of comparative sheets made from only standard southernsoftwood.

OTHER INVENTIVE EMBODIMENTS

Although the Applicants' presently desired inventions are defined in theattached claims, it is to be understood that the invention may also bedefined in accordance with the following embodiments, which are notnecessarily exclusive or limiting of those claimed:

-   -   A. A fiber derived from a bleached softwood or hardwood kraft        pulp, in which the fiber has a 0.5% capillary CED viscosity of        about 13 mPa·s or less, preferably less than about 10 mPa·s,        more preferably less than 8 mPa·s, still more preferably less        than about 5 mPa·s, or further still more preferably less than        about 4 mPa·s.    -   B. A fiber derived from a bleached softwood kraft pulp, in which        the fiber has an average fiber length of at least about 2 mm,        preferably at least about 2.2 mm, for instance at least about        2.3 mm, or for example at least about 2.4 mm, or for example        about 2.5 mm, more preferably from about 2 mm to about 3.7 mm,        still more preferably from about 2.2 mm to about 3.7 mm.    -   C. A fiber derived from a bleached hardwood kraft pulp, in which        the fiber has an average fiber length of at least about 0.75 mm,        preferably at least about 0.85 mm, or at least about 0.95 mm, or        more preferably at least about 1.15, or ranging from about 0.75        mm to about 1.25 mm.    -   D. A fiber derived from a bleached softwood kraft pulp, in which        the fiber has a 0.5% capillary CED viscosity of about 13 mPa·s        or less, an average fiber length of at least about 2 mm, and an        ISO brightness ranging from about 85 to about 95.    -   E. A fiber according any of the embodiments A-D, in which the        viscosity ranges from about 3.0 mPa·s to about 13 mPa·s, for        example from about 4.5 mPa·s to about 13 mPa·s, preferably from        about 7 mPa·s to about 13 mPa·s, or for example from about 3.0        mPa·s to about 7 mPa·s, preferably from about 3.0 mPa·s to about        5.5 mPa·s.    -   F. A fiber according to embodiments A-D, in which the viscosity        is less than about 7 mPa·s.    -   G. A fiber according to embodiments A-D, in which the viscosity        is at least about 3.5 mPa·s.    -   H. A fiber according to embodiments A-D, in which the viscosity        is less than about 4.5 mPa·s.    -   I. A fiber according to embodiments A-D, in which the viscosity        is at least about 5.5 mPa·s    -   J. A fiber according to embodiment E, in which the viscosity is        no more than about 6 mPa·s.    -   K. A fiber according to one of the embodiments above, in which        the viscosity is less than about 13 mPa·s.    -   L. A fiber according to one of embodiments A-B and D-K, in which        the average fiber length is at least about 2.2 mm.    -   M. A fiber according to one of embodiments A-B and D-L, in which        the average fiber length is no more than about 3.7 mm.    -   N. A fiber according to one of embodiments A-M, in which the        fiber has an S10 caustic solubility ranging from about 16% to        about 30%, preferably from about 16% to about 20%.    -   O. A fiber according to one of embodiments A-M, in which the        fiber has an S10 caustic solubility ranging from about 14% to        about 16%.    -   P. A fiber according to one of embodiments A-O, in which the        fiber has an S18 caustic solubility ranging from about 14% to        about 22%, preferably from about 14% to about 18%, more        preferably from about 14% to about 16%.    -   Q. A fiber according to one of embodiments A-P, in which the        fiber has an S18 caustic solubility ranging from about 14% to        about 16%.    -   R. A fiber according to one of embodiments A-Q, in which the        fiber has a ΔR of about 2.9 or greater.    -   S. A fiber according to one of embodiments A-Q, in which the        fiber has a ΔR or about 3.0 or greater, preferably about 6.0 or        greater.    -   T. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content ranging from about 2 meq/100 g to        about 8 meq/100 g, preferably from about 2 meq/100 g to about 6        meq/100 g, more preferably from about 3 meq/100 g to about 6        meq/100 g.    -   U. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of at least about 2 meq/100 g.    -   V. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of at least about 2.5 meq/100 g.    -   W. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of at least about 3 meq/100 g.    -   X. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of at least about 3.5 meq/100 g.    -   Y. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of at least about 4 meq/100 g.    -   Z. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of at least about 4.5 meq/100 g.    -   AA. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of at least about 5 meq/100 g.    -   BB. A fiber according to one of embodiments A-S, in which the        fiber has a carboxyl content of about 4 meq/100 g.    -   CC. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content ranging from about 1 meq/100 g to        about 9 meq/100 g, preferably from about 1 meq/100 g to about 3        meq/100 g.    -   DD. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 1.5 meq/100 g.        EE.    -   FF. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 2.0 meq/100 g.    -   GG. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 2.5 meq/100 g.    -   HH. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 3.0 meq/100 g.    -   II. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 3.5 meq/100 g.    -   JJ. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 4.0 meq/100 g.    -   KK. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 5.5 meq/100 g.    -   LL. A fiber according to one of embodiments A-BB, in which the        fiber has an aldehyde content of at least about 5.0 meq/100 g.    -   MM. A fiber according to one of embodiments A-MM, in which the        fiber has a carbonyl content as determined by copper number of        greater than about 2, preferably greater than about 2.5, more        preferably greater than about 3, or a carbonyl content as        determined by copper number of from about 2.5 to about 5.5,        preferably from about 3 to about 5.5, more preferably from about        3 to about 5.5, or the fiber has a carbonyl content as        determined by copper number of from about 1 to about 4.    -   NN. A fiber according to one of embodiments A-NN, in which the        carbonyl content ranges from about 2 to about 3.    -   OO. A fiber according to one of embodiments A-NN, in which the        fiber has a carbonyl content as determined by copper number of        about 3 or greater.    -   PP. A fiber according to one of embodiments A-NN, in which the        fiber has a ratio of total carbonyl to aldehyde content ranging        from about 0.9 to about 1.6.    -   QQ. A fiber according to one of embodiments A-NN, in which the        ratio of total carbonyl to aldehyde content ranges from about        0.8 to about 1.0.    -   RR. A fiber according to one of the embodiments above, in which        the fiber has a Canadian Standard Freeness (“freeness”) of at        least about 690 mls, preferably at least about 700 mls, more        preferably at least about 710 mls, or for example at least about        720 mls or about 730 mls.    -   SS. A fiber according to one of the embodiments above, in which        the fiber has a freeness of at least about 710 mls.    -   TT. A fiber according to one of the embodiments above, in which        the fiber has a freeness of at least about 720 mls.    -   UU. A fiber according to any one of embodiments above, in which        the fiber has a freeness of at least about 730 mls.    -   VV. A fiber according to one of the embodiments above, in which        the fiber has a freeness of no more than about 760 mls.    -   WW. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, as measured by wet zero span        breaking length, ranging from about 4 km to about 10 km.    -   XX. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength ranging from about 5 km to about 8        km.    -   YY. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, measured by wet zero span breaking        length, of at least about 4 km.    -   ZZ. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, measured by wet zero span breaking        length, of at least about 5 km.    -   AAA. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, measured by wet zero span breaking        length, of at least about 6 km.    -   BBB. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, measured by wet zero span breaking        length, of at least about 7 km.    -   CCC. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, measured by wet zero span breaking        length, of at least about 8 km.    -   DDD. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, measured by wet zero span breaking        length, ranging from about 5 km to about 7 km.    -   EEE. A fiber according to one of embodiments A-WW, in which the        fiber has a fiber strength, measured by wet zero span breaking        length, ranging from about 6 km to about 7 km.    -   FFF. A fiber according to one of the embodiments above, in which        the ISO brightness ranges from about 85 to about 92, preferably        from about 86 to about 90, more preferably from about 87 to        about 90 or from about 88 to about 90 ISO.    -   GGG. A fiber according to one of the embodiments above, in which        the ISO brightness is at least about 85, preferably at least        about 86, more preferably at least about 87, particularly at        least about 88, more particularly at least about 89 or about 90        ISO.    -   HHH. A fiber according to one of embodiments A-FFF, in which the        ISO brightness is at least about 87.    -   III. A fiber according to one of embodiments A-FFF, in which the        ISO brightness is at least about 88.    -   JJJ. A fiber according to one of embodiments A-FFF, in which the        ISO brightness is at least about 89.    -   KKK. A fiber according to one of embodiments A-FFF, in which the        ISO brightness is at least about 90.    -   LLL. A fiber according to any of the embodiments above, wherein        the fiber has about the same length as standard kraft fiber.    -   MMM. A fiber according to one of embodiments A-S and SS-MMM,        having higher carboxyl content than standard kraft fiber.    -   NNN. A fiber according to one of embodiments A-S and SS-NNN,        having higher aldehyde content than standard kraft fiber.    -   OOO. A fiber according to embodiments A-S and SS-MMM, having a        ratio of total aldehyde to carboxyl content of greater than        about 0.3, preferably greater than about 0.5, more preferably        greater than about 1.4, or for example ranging from about 0.3 to        about 0.5, or ranging from about 0.5 to about 1, or ranging from        about 1 to about 1.5.    -   PPP. A fiber according to any of the embodiments above, having a        higher kink index than standard kraft fiber, for example having        a kink index ranging from about 1.3 to about 2.3, preferably        from about 1.7 to about 2.3, more preferably from about 1.8 to        about 2.3 or ranging from about 2.0 to about 2.3.    -   QQQ. A fiber according to any of the embodiments above, having a        length weighted curl index ranging from about 0.11 to about 0.2,        preferably from about 0.15 to about 0.2.    -   RRR. A fiber according to any of the embodiments above, having a        lower crystallinity index than standard kraft fiber, for example        a crystallinity index reduced from about 5% to about 20%        relative to standard kraft fiber, preferably from about 10% to        about 20%, more preferably reduced from 15% to 20% relative to        standard kraft fiber.    -   SSS. A fiber according to any of the embodiments above, in which        the R10 value ranges from about 65% to about 85%, preferably        from about 70% to about 85%, more preferably from about 75% to        about 85%.    -   TTT. A fiber according to any of the embodiments above, in which        the R18 value ranges from about 75% to about 90%, preferably        from about 80% to about 90%, more preferably from about 80% to        about 87%.    -   UUU. A fiber according to any of the embodiments above, in which        the fiber has odor control properties.    -   VVV. A fiber according to any of the embodiments above, in which        the fiber reduces atmospheric ammonia concentration at least 40%        more than standard kraft fiber, preferably at least about 50%        more, more preferably at least about 60% more, in particular at        least about 70% more, or at least about 75% more, more        particularly at least about 80% more or about 90% more.    -   WWW. A fiber according to any of the embodiments above, in which        the fiber absorbs from about 5 to about 10 ppm ammonia per gram        of fiber, preferably from about 7 to about 10 ppm, more        preferably from about 8 to about 10 ppm ammonia per gram of        fiber.    -   XXX. A fiber according to any of the embodiments above, in which        the fiber has an MEM Elution Cytotoxicity Test value of less        than 2, preferably less than about 1.5, more preferably less        than about 1.    -   YYY. A fiber according to any of the embodiments above, in which        the copper number is less than 2, preferably less than 1.9, more        preferably less than 1.8, still more preferably less than 1.7.    -   ZZZ. A fiber according to any of embodiments A-YYY having a        kappa number ranging from about 0.1 to about 1, preferably from        about 0.1 to about 0.9, more preferably from about 0.1 to about        0.8, for instance from about 0.1 to about 0.7 or from about 0.1        to about 0.6 or from about 0.1 to about 0.5, more preferably        from about 0.2 to about 0.5.    -   AAAA. A fiber according to any of the embodiments above, having        a hemicellulose content substantially the same as standard kraft        fiber, for instance, ranging from about 16% to about 18% when        the fiber is a softwood fiber or ranging from about 18% to about        25% when the fiber is a hardwood fiber.    -   BBBB. A fiber according to any of the embodiments above, in        which the fiber exhibits antimicrobial and/or antiviral        activity.    -   CCCC. A fiber according to any of embodiments B-C or L-CCCC, in        which the DP ranges from about 350 to about 1860, for example        from about 710 to about 1860, preferably from about 350 to about        910, or for example from about 1160 to about 1860.    -   DDDD. A fiber according to any of embodiments B-C or L-CCCC, in        which the DP is less than about 1860, preferably less than about        1550, more preferably less than about 1300, still more        preferably less than about 820, or less than about 600.    -   EEEE. A fiber according to any of the embodiments above, in        which the fiber is more compressible and/or embossible than        standard kraft fiber.    -   FFFF. A fiber according to embodiments A-OOO, in which the fiber        may be compressed to a density of at least about 0.210 g/cc,        preferably at least about 0.220 g/cc, more preferably at least        about 0.230 g/cc, particularly at least about 0.240 g/cc.    -   GGGG. A fiber according to embodiments A-OOO, in which the fiber        can be compressed to a density of at least about 8% higher than        the density of standard kraft fiber, particularly ranging from        about 8% to about 16% higher than the density of standard kraft        fiber, preferably from about 8% to about 10%, or from about 12%        to about 16% higher, more preferably from about 13% to about 16%        higher, more preferably from about 14% to about 16% higher, in        particular from about 15% to about 16% higher.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the disclosure. Accordingly, other embodimentsare within the scope of the following claims.

We claim:
 1. A method of making a kraft fiber comprising: bleaching acellulosic kraft pulp using a multi-stage bleaching process; andoxidizing the kraft pulp during at least one stage of the multi-stagebleaching process with a peroxide and a catalyst under acidic condition;wherein the multi-stage bleaching process comprises at least onebleaching stage following the oxidation stage; and wherein themulti-stage bleaching process has no alkaline stage following theoxidation stage.
 2. The method of claim 1, wherein the catalyst ischosen from at least one of copper and iron.
 3. The method of claim 2,wherein the peroxide is hydrogen peroxide.
 4. The method of claim 3,wherein the pH of the oxidation stage ranges from about 2 to about
 6. 5.The method of claim 4, wherein the catalyst is iron.
 6. The method ofclaim 5, wherein the iron catalyst is chosen from at least one offerrous sulfate, ferrous chloride, ferrous ammonium sulfate, ferricchloride, ferric ammonium sulfate, or ferric ammonium citrate.
 7. Themethod of claim 6, wherein the iron catalyst is added in an amountranging from about 25 to about 200 ppm iron based on the dry weight ofthe kraft pulp.
 8. The method of claim 7, wherein the pH of theoxidation stage ranges from about 2 to about
 5. 9. The method of claim8, wherein the hydrogen peroxide is added as a solution at aconcentration of from about 1 to about 50% and in an amount of fromabout 0.1 to about 4% based on the dry weight of the pulp.
 10. Themethod of claim 9, wherein the hydrogen peroxide is added in an amountof from about 0.1% to about 1.5%, based on the dry weight of the pulp.11. The method of claim 9, wherein the iron catalyst is mixed with thekraft pulp at a consistency ranging from about 1 to about 15%.
 12. Themethod of claim 11, wherein the oxidation stage is carried out at atemperature ranging from about 60 to about 80 degrees Celsius, and for atime ranging from about 40 to about 80 minutes.
 13. The method of claim11, further comprising the addition of heat, either before or after theaddition of peroxide.
 14. The method of claim 13, wherein the additionof heat is in the form of steam.
 15. The method of claim 9, wherein themulti-stage bleaching process is a five-stage bleaching process andwherein the oxidation stage is the fourth stage.
 16. The method of claim15, wherein the fifth stage comprises treatment with chlorine dioxide.17. The method of claim 15, wherein the five-stage bleaching processcomprises a sequence of D₀E₁D₁E₂D₂, and wherein the oxidation occurs inthe E₂ stage.
 18. The method of claim 4, wherein the oxidation stageincreases the carboxylic content, the aldehyde content, and the ketonecontent of the cellulose fiber.
 19. The method of claim 4, wherein theoxidation stage causes a decrease in the crystallinity index of thecellulose fiber of up to 20% relative to the starting crystallinityindex as measured before the oxidation stage.
 20. The method of claim 4,wherein the bleaching process causes a reduction of the 0.5% CapillaryCED viscosity of the cellulose fiber.
 21. The method of claim 20,wherein the 0.5% Capillary CED viscosity is reduced to less than about 5mPa·s.
 22. The method of claim 20, wherein the 0.5% Capillary CEDviscosity is reduced to a range from about 3 to about 7 mPa·s.
 23. Themethod of claim 4, wherein the modified kraft fiber can be compressed toa density of at least about 8% higher than the density of a standardkraft fiber that is identical in composition to and processed in a samemanner as the modified kraft fiber, but without having been subject toany oxidation.
 24. The method of claim 23, wherein the increase incompressibility is at least about 14%.
 25. The method of claim 4,wherein the modified kraft fiber reduces at least about 40% moreatmospheric ammonia than a standard kraft fiber that is identical incomposition to and processed in a same manner as the modified kraftfiber, but without having been subject to any oxidation.
 26. The methodof claim 25, wherein the modified kraft fiber reduces at least about 60%more atmospheric ammonia than a standard kraft fiber that is identicalin composition to and processed in a same manner as the modified kraftfiber, but without having been subject to any oxidation.
 27. The methodof claim 1, wherein the multi-stage bleaching process is a five-stagebleaching process and wherein the oxidation stage is the fourth stage.28. The method of claim 27, wherein the fifth stage comprises treatmentwith chlorine dioxide.
 29. The method of claim 27, wherein thefive-stage bleaching process comprises a sequence of D₀E₁D₁E₂D₂, andwherein the oxidation occurs in the E₂ stage.